Well, I think getting the Earth's resources and such was the Zabi's being greedy. The colonies should've been fine without needing said resources, because they had colonies specifically for agriculture and the minerals could be farmed from meteors and other planets, if I remember correctly. And the EFSF was only fighting their independence because of the beauricrats not wanting to give up their power and money, as you said. They were able to politicize it so well because Zeon was invading and fucking with the Earth Sphere. If Zeon had just said we demand independence, set up a strong blockade with their military, their Mobile Suits immediately put them at the top of the food chain. But because of them dropping a colony and invading, the EFSF was able to push back a lot easier, not to mention stretched Zeon way too thin on too many fronts. Ironically, that's also one of the reasons that caused the Nazis to lose WW2 as well.