Lunaris lost because he focused too much on Scrooge and his allies, not his enemies like Glomgold.
Except there is one ally of Scrooge's the Moonlanders weren't prepared for: Darkwing Duck. His show's been off the air for years, his original actor is presumed dead, and the movie that would have reintroduced him to the public got canceled before anyone outside of a very niche fandom even knew about it. Drake Mallard as Darkwing hasn't done anything big enough yet to put himself on TV where Lunaris could see him. DW wasn't a factor in any of Scrooge's plans. In fact, Scrooge didn't even remember Darkwing existed, let alone who he was, despite both of them riding in the same vehicle. The only reason DW was involved at all was he overheard Scrooge's message to Launchpad and tagged along with him. The Moonlanders have never heard of Darkwing Duck, and therefore have no plan of action against the "purple weirdo" showing up out of nowhere. So when he makes his entrance, they ignore him.
Lunaris was paying attention to Glomgold. Look at the globe in his secret war room found by Phenumbra and Donald in "What Ever Happened To Donald Duck." One of the pictures is on Glomgold, but look back at what happened in between, Glomgold was tricked by Louie into losing all of his resources at the end of "GlomTales". Lunaris must have stopped thinking of Glomgold as a threat since he had no resources to be a threat.
Glomgold would in fact be the worst kind of enemy for Lunaris to go against. Having studied Scrooge extensively the general would know that Scrooge favors a Boring, but Practical approach and would plan around that accordingly. He would not do as well against Glomgold however as the latter's Complexity Addiction would translate into Confusion Fu as Lunaris would simply be unable to grasp every chaotic intention in said plans. Scrooge does not have this issue as he's been dealing with Glomgold for years and knows how to see through his convoluted schemes.
Lunaris likely disregarded Gladstone and Fethry in his plans because Scrooge keeps them at arms length on the best of days, owing to Gladstone being insufferable and Fethry being scatterbrained. He didn't regard them as an issue because he never thought Scrooge would call on them for help. This also meant that he was unaware of the resources they could bring to Scrooge's aid, given how he knew nothing about Mitzi.
Lunaris had good reason not to concern himself with Scrooge's enemies. He would know that Scrooge is immensely prideful and would never consider an Enemy Mine situation unless things became incredibly dire and by the point he may be willing to engage in one it would be too late to do anything. Unfortunately for him Glomgold was just unpredictable enough that he couldn't salvage things once they went wrong.
Lunaris never meant to target Scrooge's family; having been spying on them all this time and living with Della for over a decade, he knew that Scrooge's and Della's rational judgement takes a nosedive whenever their family is in danger and their competency in keeping them safe is put to question. So he threatens them knowing this will completely mess them up: minimal effort, maximum effect. He didn't need them out of the picture, he just needed Scrooge and Della to be so focused on protecting the kids that they'd be distracted from dealing with him. What he didn't account for was Donald, who was the opposite of the two and became hyperfocused and superstrong when his family is endangered, and Glomgold, who is completely unphased by...pretty much anything.
The reveal of F.O.W.L. High Command posing as Scrooge's own board of directors makes perfect sense from a criminal standpoint, as there's no better way to gain the money you need to commit your and your partner's crimes than by embezzling the funds of your employer. With Scrooge being the richest person in the world, and whose business and ventures likely make him so much money, he probably hasn't been noticing that some of the money he makes from his practices (sans treasure hunting) has gone missing.
It also makes sense as to why they were so dead set on stopping Scrooge from spending all of his fortune on finding Della when she disappeared into outer space: they weren't concerned with the company going bankrupt or Scrooge's wellbeing, they were concerned that all the funding he was putting into tracking down his niece would leave them with less money to use to benefit F.O.W.L.
Another factor is that Della's loss, and Scrooge's subsequent failure to locate her, sent Scrooge into a depression that kept him out of commission for a decade. While he wasn't a dedicated enemy of F.O.W.L., he still worked with S.H.U.S.H. and was an occasional thorn in their side. Scrooge in his Heroic BSoD was one less problem they had to deal with.
Plus, this puts their business strategy of "being cheaper than I am" in a new perspective. Since F.O.W.L. is an organization of thieves, they would believe in taking more from an existing thing than building something new. Hence the strategy to cut rather than invest.
It may also show why previous episodes show them so eager to cut funding for the defensive magic & technology that Scrooge has. They are trying to weaken Scrooge's defenses!
Gandra being part of F.O.W.L. likely means that she was only working for Mark Beaks as part of an assignment, likely to spy on him. Considering that Beaks is a tech mastermind (he appeared with Boyd six episodes prior), he is a potential threat to the organization.
Or she could just be a Punch-Clock Villain like she was before with Beaks. Only F.O.W.L. offered a bigger paycheck to work longer term.
There's another option. She was checking to see if they could RECRUIT him, seeing his complete lack of ethics. The fact that he's an idiot, means the answer is no.
Black Heron survived her Disney Villain Death because while the effects of the Gummiberry juice formula she took during her fight against Webby might have worn off as she fell, grabbing the edge of her hideout with her robotic arm (while detaching herself from it) probably slowed her fall enough for her to land safely into the ocean below without being fatally injured.
Funso’s mascot, really the Phantom Blot in disguise, being part of F.O.W.L. explains why he was so casual interacting with someone as Obviously Evil as Magica. As for why he took this identity, The Phantom Blot is a Master of Disguise, and he'd pose as the mascot to check on Magica and evaluate her as a possible ally, or/and to keep an eye on Webby and Scrooge's nephews, once F.O.W.L. learned that they were regular Funso's clients.
The fact that the Mascot is a walrus also acts as an homage to Tuskernini, also a walrus from the original series, who was originally conceived as a F.O.W.L. operative, if only to fulfill a reference to The Beatles.
Donald got his vacation, but with his luck it was not the one he wanted nor the one he needed.
Gladstone's appearance isn't just a coincidence. His ridiculous luck would definitely keep him safe from The End of the World as We Know It, which, in this case, could only happen by giving him a role in preventing it.
This also ties into how Della and the kids somehow managed to crash land on the exact same deserted island Donald did. Again, Gladstone's luck brought his family back together in order to thwart The End of the World as We Know It.
They don't comment on it, but this time it's Gladstone rescuing Donald (and Co.) from a inescapable situation.
Each of the kids do reflect the adults whose poses they're mirroring:
Della and Webby are the Action Girl of the group who love adventures. Louie and Gladstone are the laidback ones who'd rather not do a whole lot of work. Huey and Fethry already had an entire episode together showing their similarities. For Dewey and Donald, they love their family and would go to great lengths to keep them safe.
Dewey laments that he is Donald, who is generally the buttmonkey of the four. However Donald is also the one that's a hidden badass who is often underestimated by others because they don't fully understand him, which can also describe Dewey come season 3 (when he turns out to be quite a skilled pilot). Furthermore, he also has a closer working relationship with Webby when it comes to adventuring, mirroring how Donald and Della were the ones who adventured with Scrooge rather than Fethry and Gladstone.
Duckworth, when heading to the afterlife to prepare the Duck family's new residence, goes downward instead of upward, which is Lampshaded by Beakley. However, this does not necessarily mean they are going to Hell when they die - since the Duck universe runs on an All Myths Are True logic, there can easily be an afterlife for good people in the Underworld. After all, let us not forget that Zeus has a certain brother named Hades....
The reveal of F.O.W.L. after the big group shot of the new "expanded" Mcduck clan provides another incentive for the organization to get moving against the Ducks/Mcducks: Their ranks have expanded to include two superheroes (one Badass Normal and another with Powered Armor), two new Kid Hero sidekicks, the cousins reconnected, Donald and Della coming back around, and an alien in their midst. With a more limited number of "lead" members, F.O.W.L. seems to have started to realize just like Glomgold's Legion of Doom that Scrooge is becoming too powerful to stop if they don't start acting now.
Beakley calling Glomgold out on forcing Scrooge to dress like Santa wasn't just for a You Monster! reaction. Given how bad things are and her being the Only Sane Man next to Scrooge she's genuinely aghast that Glomgold is being so petty when they have much bigger worries.
How does Scrooge know Darkwing Duck’s catchphrase? With Launchpad and Beakley being fans of it, one or both were bound to show him some episodes. Becomes Heartwarming that Mr. McD would remember it.
It could also have something to do with the unreleased Darkwing Duck film he attempted to produce earlier in the season. While that episode showed him having little interest or desire to finance a feature film, it's plausible to assume Scrooge at least did enough research on the original show to understand what he was getting involved in and what the basis of Alistair Boorswan's film was.
Scrooge notably has a confidence issue whenever protecting others comes into play, but in the final fight he has no problem bringing the kids, Della, and Donald into the fight, even being the commander of the ship with a cool head (while Donald and Della bickered). This is because, with Donald being away for most of the season, this is the first time his family was truly complete. With his entire family back with him, the trauma of losing Della and all the mistakes that followed are now gone.
More importantly, McDuck Enterprises is a huge, and powerful institution, so any employee could possibly be a F.O.W.L. agent.
A nefarious criminal organization that has infiltrated the main force of good (though not S.H.U.S.H. in this case...hopefully) for a long time, in a setting that has combined updated versions of many previously-unconnected media of the same company. Where have we seen this before?
With no sign of food on board his ship, Lunaris is fated to a slow death via starvation.
The only other living being on his ship is the shark in a parka. Which means Lunaris will probably kill and eat the shark to survive (or simply wait for it to die of asphyxiation from being away from water for too long). Of course, he'll still end up starving to death after he finishes that shark, since it's his only food.
Then again there's a pretty good chance that at least some of the Moonlanders will want to go back home after they realize how much Lunaris lied to them about Earth and it's intentions. If they do then there's no reason to think they wouldn't want to pick him up and take him back with them to see him face proper punishment, especially if Penny has anything to say about it given what he did to her
Not to mention Selene's appearance. The Greek gods (if not Selene specifically) were known for doling out ironic punishments, so it's not impossible that she granted him some degree of immortality in order for him to really suffer. Granted, the likes of Sisyphus and Tantalus were already dead when they received their karmic comeuppance... so maybe Lunaris is too.
There's no food on the Moon to begin with, the Moonlanders likely don't need to eat much or at all.
