Why exactly is it that the Rabbids have managed to integrate into Mario's society so well, despite their past outings having them wreaking havoc and causing problems? Even with the merging aspect taken into consideration, there's still a number of Rabbids that seem to be unchanged physically. There's actually a number of reasons:
1) The Mario world is no stranger to odd creatures and races. A lot of races in the Mario universe are not exactly any less full of their own bizarre cultures and beliefs, and thus in many ways the Mario world is infinitely more compatible with the Rabbids' eccentricities than their past homes.
2) The typical residents of the Mushroom Kingdom aren't as hostile towards them. While admittedly it's also partially the Rabbids' fault for being so destructive and antagonistic in the past, their past homes didn't exactly make any effort to see them as anything except dangerous creatures, meaning that they in turn have no reason to try to be hospitable or caring. Even Rayman saw them as dangerous and something for him to avoid, albeit for understandable reasons, which takes him a bit to get over in the DLC. The Mario universe by contrast, tends to lean towards generally kinder and more open personalities (even Bowser on occasion), and combined with the circumstances of their coming into this Mario world, the Rabbids simply don't have much reason to ''be'' destructive.
3) A combination of the merging process and the above has caused the Rabbids to develop greater intelligence overall, making them more empathetic overall, albeit still kooky weirdos. Something to note about the Rabbids is that while they're usually seen as Chaotic Stupid in the past (not unjustly), they were still intelligent enough to understand how to use a number of objects with minimal difficulty, and even adopt cultural interests like dancing. Their biggest problem more than anything seems to be that they didn't understand or care about the feelings of those around them, which meant that when their antics caused numerous problems, they were not capable of understanding what they did wrong. The merging process with various objects seems to subjected them to the memories and feelings of whatever they're fused with, such as the Phantom of the BWAAAHpera having resentment, jealousy, and feelings for Princess Peach. This, combined with the above of the Mushroom Kingdom being more open and less likely to ostracize them for their oddities, seemed to have not just improved their regular intelligence, but also seems to have boosted their emotional intelligence as well. Because of this, they're more able and willing to care about others, and thus actually develop more complex relationships and choose to be less of a nuisance.
Both Bedrock and Midnite appear to be more morally complex than Daphne is. Midnite allowed Rabbid Rosalina to roam free in her Darkmess Dimension area and read the books there rather than trapping her in containment spheres, Bedrock has a sense of respect for Bowser in combat, both of them were more impacted by Edge's betrayal than Daphne was, and both of them look uncomfortable during Cursa's absorbance of the Sparks. In comparison to Midnite and Bedrock being the results of fusion of Rabbid DNA with "a cold mist during the dead of night that chills to the bone" and granite rock respectively, Daphne is the result of fusion between Rabbid DNA and a species of pink climbing rose. Having more biological data to work with during her creation could have allowed Cursa to instill a higher level of loyalty to villainy and her cause, as we've seen from Edge herself that Cursa could manipulate the mental state of her minions while creating them.
Why on earth did JEANIE just happen to have a weapon that was designed with Bowser's specs in mind? Even if Rabbid Mario was the one intended for it, it's very odd that they would just happen to design it with his appearance in mind. But that's actually what makes it brilliant; Rabbid Mario is the one it was intended for, so it's possible that Rabbid Mario wanted it to be intentionally modeled after Bowser. One of his major character traits is his tendency to act like a macho man (er, bunny), and he's seen Bowser before. Bowser's physical appearance oozes masculinity and coolness, especially to someone like Rabbid Mario. So of course he'd end up asking for a weapon based on someone that physically imposing. Of course, being a Rabbid, he probably didn't exactly consider that building a weapon according to Bowser's specs might end up making it far too big and heavy for someone barely a fraction of Bowser's size.
Why didn't the Spark Hunters show up again after their initial defeats? None of them were permanently defeated as far as we could tell, and it is definitely odd how they did not even attempt to stand between Cursa and their enemies including their old leader, Edge. Even ganging up together would have given them a far better chance of at least slowing down Mario and his friends. After thinking about it however, it actually does make some sense:
1) They are too outclassed at this point, and the majority of them have strong self-preservation instincts. They're keenly aware of just how dangerous Mario and his friends are against any one of them, and even if they fought together, their opponents have only gotten more powerful since the start of their journey, meaning that the risk of losing or worse is even greater. With Cursa's defeat imminent, and each of them having fallen out of favor with Cursa with their failures, they may have decided to cut their losses and flee.
2) Cursa can't risk them working together to fight against Mario and his friends, because their conflicting loyalties and lack of cohesion makes them dangerous to themselves and each other. Trying to work together would have been very difficult for them in part because of the differing opinions towards their former leader, and because of their incompatible personalities. Midnite and Bedrock have the most conflicted feelings towards their former friend Edge, which would have made them a potential liability or possibly be swayed if they decide that their friendship outweighs their fear of Cursa. Daphne on the other hand is completely fine with annihilating Edge, which would have put her in conflict with the other two Spark Hunters.
3) Cursa can't do anything to really force them to be more cohesive, because of the risk of them turning against her and in part because of what happened to Edge and later, Kanya. Cursa was able to get away with her power over them because they were united in a common goal of stealing the Sparks and empowering her. But Edge's defection and Kanya going into business for herself threw things completely off for all of them, engendering conflicting loyalties and the loss of cohesion between the Spark Hunters. And Cursa can't risk giving any of the remaining Spark Hunters the same free will and intelligence that she had given to Edge and Kanya, because there always exists the risk that it would only result in the exact same thing happening again to her remaining inner circle, thus bolstering her opponents even more.
4) Cursa is already expending too much energy trying to keep her position of possessing Rosalina under control. She understands just how fickle and difficult brainwashing can be on stronger souls like the Spark Hunters. And given how Rosalina has broken out of her control several times throughout the game, even if only briefly, Cursa is likely dedicating all of her energy to keeping things in check. As such she simply doesn't have the power to expend on trying to maintain absolute control of her inner circle and her situation simultaneously without risking one or the other breaking free.
By the beginning of the game, all of the heroes already have weapons that are way more reliable than the ones they had in the previous game and their starting HP is higher as well. This is because the heroes had enough time between Kingdom Battle and Sparks of Hope to prepare stronger weapons and they still retained their experience from the previous game, averting the recurring Bag of Spilling trope.
It's also likely that they've had plenty of time to figure out not just how to get stronger weapons, but more importantly weapons that are better fitting to their preferred fighting styles, instead of just using only what they have on hand.
Bowser being able to summon Mechakoopas instead of his other known minions makes sense when these types of minions are mechanical in nature, programmed to only obey the Koopa King, and are thus immune to Cursa's brainwashing, which stole away his army in the first place.
What's especially interesting in this game is how much each of the Wardens and locations are thematically linked to the major obstacle or Spark Hunter of their respective levels:
Beacon Beach is the starting level, with Augie being the Warden. Augie being a fearful Rabbid makes this area one of the worst off in terms of defending against Cursa's forces, but this is counterbalanced by the fact that the first major obstacle is no longer an actual problem due to Edge defecting from the Spark Hunters, thus ensuring the easier level. Furthermore, a major gimmick of the area is using light to uncover new locations, much like how Edge showing up allows her to shed more light on Cursa and the Spark Hunters and improving Mario's team chances.
Pristine Peaks is next, with Captain Orion as the acting Warden. The major obstacle is initially the blizzard, but the overall threat is the Spark Hunter Midnite. Her character parallels Captain Orion, in that her major thematic link is in regards to complicated relationships with someone they care for. In this case, her own complicated feelings of betrayal and sadness towards Edge's defection, and Captain Orion's love and protectiveness towards Rabbid Rosalina. The endings of said relationships are also different, with Midnite's complicated friendship ending decisively with Edge making it clear that they aren't on the same side anymore, while Rabbid Rosalina and Captain Orion part on good terms. Edge's own complicated relationship with the rest of her new allies is also another consideration, given how she keeps everyone at a distance and she's still keeping a lot of details about herself secret.
Palette Prime's is a bit more straightforward. The focus on poetry with T.S. Woodrow leans towards a very intellectual and artistic bent, which becomes a direct counterpoint to the obstacle of this area, the Spark Hunter Bedrock. Both she and Bowser represent raw power and strength, and it's made pointedly clear that trying to fight her head on is ultimately a exercise in futility due to her sheer durability. Instead, the primary way to fight against her is to exploit her flaws in her fighting style, using intellect and cunning to defeat her.
Terra Flora is a bit more vague to figure out, but leans more towards the restoration of nature. The Warden Bea grants you the ability to use vines in order to progress further, but the major obstacles are resolved in somewhat opposing ways, with Sullivan providing you with the means to reach the source of the problem using technological means (his steam engine), while the ultimate obstacle being to destroy a Darkmess Dam in order to release the water back into the area.
Barrensdale Mesa leans heavily towards the theme of honesty and deceit with its Warden Momma and the final Spark Hunter, Daphne. Momma is impatient with deception and those who waste her time, being a very straightforward and sarcastic woman who only agrees to help if given aid in return. However, she and Mario's team are caught off guard by Daphne, who manages to capture Momma, and disguise herself as the Warden in order to lure Mario and friends into a trap. Further continuing the theme of deception is Daphne further confronting Edge about her true nature, and Cursa's unexpected confrontation revealing the truth about her possessing Rosalina.
The Melodic Gardens are another straightforward one. The Warden, Allegra, is a soft-spoken, serious Rabbid who's a Friend to All Living Things and can use her tuning fork to control the gardens to some extent. Kanya, naturally, is the opposite: a Large HamGadgeteer Genius who hates nature and wants to tear apart the gardens for materials. It also serves as an inversion to the Barrendale Mesa: while Daphne was a nature-based Spark Hunter in the mechanical Mesa, Kanya is a mechanical-based Spark Hunter in the natural Gardens.
Several of the Warden's stories imply that said Wardens have been around for years, long enough to have been children (namely that of Augie, whose story follows him from birth). This is a bit odd, given that their deviations from traditional Rabbid biology would imply that it's the result of the Supa Merge or something similar from the first game, but not enough time would have passed for them to have lived those lives, especially considering they appear to be of similar age to Mario and company. So how can this be? Simple, the Rabbids have a time machine. Several of them could have went back in time, maybe to better establish themselves on their respective planets or by accident, thus creating the circumstances for several wardens to be born prior to the events of the first game as their unique selves.
Why was the Phantom roasting Rayman the most in The Phantom Show? He's a mixture of a Boo, a gramophone, and a Rabbid. We know that the Rabbids and Rayman have beef with each other, but while Rabbid Peach and Mario got over their distrust with him, the Phantom never does get over his animosity.
Cursa's name has a bit more meaning to it than it might seem to at first. It's obviously derived from "curse," but there's also an actual star named Cursa, fitting the game's space theme. Even better, it's in close proximity to the constellations Lepus (a rabbit) and Orion (as in Captain Orion).
, fitting the game's space theme. Even better, it's in close proximity to the constellations Lepus (a rabbit) and Orion (as in Captain Orion).