Reading some ScroogeMcDuck comics coincidentally after reading Daisy Miller got me wondering — Could John D. Rockerduck's popularity in Europe somehow be related to the traditional "old money vs. new money" conflict between old European and American values? Glomgold may be a dishonest Corrupt Corporate Executive, but he is a Self-Made Man like Scrooge. Scrooge's conflict with someone who inherited his fortune like Rockerduck might be more significant to Europeans. Or I could just be far too presumptuous.
I think you're reading far to much into that. In fact, I, even though I'm an European, prefer 'self-made men'. Times changed, I do not believe that the Europeans still (if they ever did as a whole group) find someone who inherited his fortune more important. ('Cept maybe the English.)
What's funny is you got thing the wrong way around. Sure, Rockerduck inherited his money while Scrooge is a self-made man, but most modern depictions of their rivalry are rather around the lines of Rockerduck as a modern businessman who gets money from investments, buys yachts and high-tech gadgets, is all about fashion and the picture people are getting from him, in fact acting more like a real-life present-day billionaire, whereas Scrooge is an "old-fashioned" billionaire who keeps his money in the form of cash, sits on it, is stingy, made his money "square" with "his bare hands" and doesn't care about the opinion people have of him as long as it's not an obstacle to him winning money. Rockerduck incarnates modernity with all its wasting, its pointless vanity and its smugness, while Scrooge is the incarnation of "good old times" where public opinion wasn't a big deal and people made their money with their bare hands, and then kept their money without boasting about it. In a nutshell, paradoxically, Rockerduck's more the "new money" and Scrooge the "old money", in another meaning of those two words.
Don Rosa writing a Kalevala-themed adventure for the Ducks was highly appropriate. As the comic says, Elias Lönnrot wrote the The Kalevala by compiling various Finnish myths, legends, and poetry together — exactly what Don Rosa did with The Life and Times of Scrooge McDuck. It's a fitting reminder of how all the great epics were written, from 700 B.C. to 1992.
In real life, Scrooge would've run out of business quickly. His workers and families will quickly figured that working for ANYONE else will bring much more money and less headaches. Or worse, he will go to jail sooner or later when someone sued him for pay his workers at much more lower than minimum wage. However, since he owned nearly any kind of company (from resorts to oil refinery), he can get away with it since he contributed so much to taxes and people lives that he's practically invincible to law, and people who starved for job will still work with him anyway. The effect is showed in some of Don Rosa and Carl Barks' comics, where Scrooge's showed as the only man in Duckburg that able to pay things like Rocket Project and giant robot's production cost.
On the other hand, he pays so little to Donald... because it's time off for him. He doesn't consider it 'real work', he simply covers the time lost by Donald when on treasure hunts, but since Scrooge is an explorer, he also considers the treasure hunt to be a reward in itself... Or at least this is what he'd tell Donald!
Scrooge pays little, but he pays well enough and makes sure his workers won't need much more money thanks to side benefits.
It's pretty much shown time and again that Scrooge owns nearly every business in Duckburg. So there's not really any getting around working for him. Only difference is that some people work directly under him within his Money Bin and others work far away at one of the various businesses he owns.
Why is Rockerduck so obsessed with defeating Scrooge? Two reasons: the first is that he usually comes as the second richest by very little but he also spends more, and given his standard insult to Scrooge is pointing out he's a tightwad the fact he's less rich because he's not as much as a skintflint obviously burns; the other is that Rockerduck's own father taught Scrooge how to be a prospector, and he most likely knows (he had all the elements to guess it. All he needs to do is to check the records for the name of the prospector who staked a claim to the Anaconda Copper Mine...).
Dolly Duck, AKA Fantomius' accomplice and fiancee Dolly Paprika, is a cousin of Dabney Duck, AKA Donald's grandfather, and the daughter of a "Samantha Gander". This explains many things in both Paperinik's stories and Fantomius' own series:
Donald taking Fantomius' legacy and becoming Paperinik after finding Fantomius' journal: he not only was a child when Fantomius was active, but likely heard his stories from Fantomius and Dolly themselves. Finding the journal, that reveals Fantomius' identity and starts by hoping someone will take his mantle, was him finding out he was in-laws with his childhood hero and being asked by him to take up his legacy.
In Ultraheroes Paperinik and Paperinika have another of their fights when Paperinika muses that Dolly Paprika was the main reason for Fantomius' success and Paperinik takes offence. He knew that Fantomius' own genius was the main reason for their group's success because Dolly himself had told him when he was a child.
At the end of "Il Ladro e il Miliardario" ("The Thief and the Billionaire") Fantomius, who has made an attempt at Scrooge's money when he was temporarily back in Duckburg in 1922, sent Scrooge a message telling him he wouldn't touch the money as long as he was away and the Money Bin was in Mathilda and Hortense's care, but once he came back he'd steal even the bed he's sleeping on (as Scrooge returned for good after Fantomius' disappearance, Paperinik had to keep the promise). Why this strange limit? He had likely heard of Scrooge's one criminal action in Africa and that his sisters had practically disowned him for it, leading him to consider Scrooge no better than the "thieves disguised as gentlemen" he usually targeted but wouldn't let his sisters, who had tried and failed to stop him, risk being hold responsible for failing to protect the money.
Lord Quackett's (AKA Fantomius) estate was acquired from the state because he had no heirs, leading to his manor becoming the prize of a lottery and ultimately ending in Donald's hands due a mailman's error. Either lord Quackett and Dolly never married, or they married and Gladstone, being the closest relative, inherited the lot but refused it for some reason.
In Paperinik stories Gyro has created memory-erasing candies by his own initiative, and by his own decision takes one whenever he learns Paperinik's real identity (Donald actually revealed him he was Paperinik in the second Paperinik story, and Gyro immediately revealed the existance of those candies and took one specifically to forget it). Considering that Gyro's great-grandfather was Fantomius' personal Gadgeteer Genius and they had a few misadventures due his real identity getting out...
When Scrooge came back Duckburg as the (unknowing) richest duck in the world in 1930 he was furious, and when he found out he was the richest duck in the world he could not believe it. This makes absolutely sense when you remember Scrooge's favouritism for possession of cash and that most of the damage in the Great Depression had been caused by bank panic started in late 1930: he had just given his banks with the money they needed to survive the bank runs that were happening right at that very moment, and while that meant his financial empire had survived and would grow on the long run he probably believed he had just thrown away his lifelong dream of becoming the richest in the world and could not continue his travels to make a final try. Hence his rage (and one final fight with his sisters) and surprise when he discovered that, even after the bank runs had already reduced his net worth, he was still the richest duck in the world.
At the start of the "Amazing Files" series, a sequel of the Italian stories about Donald's childhood, Donald is quick to realize that the coincidences that brought him to own the sci-fi magazine Amazing Papers (that he was an avid reader of as a child) actually mean something and that the strange informations contained in the titular amazing files may be true, but his childhood friend dismiss it as too similar to the stories he came up as a duckling (at least until they get involved and actually meet the strange happenings) and initially tell him to grow up. He did, it's just that Donald has found the Holy Grail (and broke it on the head of a villain), found El Dorado, met the Grim Reaper and laughed in his face to brag that Donald Duck laughs in the face of death, has an alien Love Interest, and so on-to him it's just a typical wednesday.
Donald supports Scrooge and Goldie because he sees it could (and should) have worked out, had they just talked to each other back in the day, and still have feelings for each other. He also supports Brigitta with anyone else because he wants his uncle with Goldie, and Brigitta deserves a break.
Scrooge supports Donald with Reginella because he compares Donald and Daisy to himself and Goldie and can see their communication problems, problems that are completely absent with Reginella.
The two times they met on-page, Goldie told Brigitta to pursue Scrooge because she already had some happiness from him (one of those meeting was Dickie's debut story, with everything implying that Dickie was also Scrooge's granddaughter), and Brigitta had suffered far more than her from her devotion to Scrooge.
If the theory about their father being Daisy's brother, Huey, Dewey and Louie support her with Donald because this way they'd symbolically have their parents back. They likely don't realize this.
Scrooge is so tough on Donald because his immense array of skills proves he's just as good if not better than Scrooge was in his youth, yet Donald won't bother to work it off long enough to become rich, thus, in Scrooge's eyes, wasting his potential.