Where and how does Eggman get all his resources? You'd have to have full communistic control of an economy to pull of his stunts! It makes sense in Satam and with Robotnik, but Eggman (who has never succeded where Robotnik has triumphed, taking over Sonic's home)...
That's where you're wrong.
Considering he has Massive Amounts of Animals Trapped In Robots, huge machines of death, and has a few times brought the world to his knees, clearly Eggman has some Success. Evidence even more in Shadow the Hedgehog where his troops are able to hold their own against GUN and Black Arms. Sonic may be beating Eggman, but that doesn't mean he hasn't won when Sonic wasn't there.
Also Consider that he does have massive amounts of Robots. Many like the Burrow Bots don't appear to be for combat purposes, meaning there is a chance he actually gathers his own Resources. Example the Lumberjack Robot from Sonic and Knuckles, he's able to fight but appears to be more designed for cutting down trees, which are probably used by Robotnik in some way.
He also did create an intergalactic Theme Park which at one point was going to be opened to the public. Likely he has some connections financially that both help him pay for these things, allow him to make money, and bribe some legal system, because there was no way in heck I would trust someone who threatened to blow up a country enough to go to his theme park.