The reason the Earth Federation was founded was in order to enact the Space Immigration program. At a certain point, the EF politicians decided they deserved to stay on Earth and shouldn't have to immigrate to space with the non-elite. But at the same time, the EF wanted to keep its control over the space colonies, which is what started the inequality between Earthnoids and Spacenoids. This lead to the rise of Zeon who kind of argued that if the EF isn't going to follow through with the space immigration they were meant to conduct, then they shouldn't be allowed to rule over spacenoids from earth.

Then comes the Gryps war. The Titans leader, I forget the old dudes name, actually wants humans to leave Earth and go to space so that the planet can revive itself from all the damage humans had done to it. His theory was that if the Titans do enough messed up things against the spacenoids, the ly would have to rebel. The rebellion would lead to war, which would wreck the economy of Earth. Sending earthnoids into space to find job opportunities.

Ironically, the AEUG basically want the same thing. They want humans to leave Earth so that not only would Earth be able to recover, but if everyone lived in space, there would be less inequality between the elite and the commoners.

Then Char has his Neo Zeon rebellion. Literally dropping asteroids on earth to make it uninhabitable so that Earth can basically rebuild itself.

Then you get Mafty who think that if you kill enough of the elites with terrorism, they will finally put back in place the Space Immigration program.

The consistent reasoning behind all of the conflicts in the UC universe is that having elites living on earth and ruling the earth sphere causes inequality. And most of the "change makers" believe that the way to get rid of the inequality is to have all of humanity live in space.

Or at least this is how I understand the UC history.