Dude the Wehrmacht reached a town called Krasnaya Polyana which is 18 miles away from the center of Moscow. If they took over Moscow, which was a very real possibility then the Soviet Union would’ve fallen like France, or at the very least the European portion of it would.
That's not how capitals work. France itself only nominally fell because it appointed an ultraconservative collaborator (Petain) to the highest position of government.
I would assume the oppressed minorities within the empire would used them opportunity to get independence.
Most of the oppressed minorities were in Nazi-occupied Eastern Europe, and very quickly found out that the Nazis were no liberators. Most of the remaining Soviet population was Russian, not ethnic minorities. A few of the central Asian SSRs were around, but their governments weren't oppressed, but participants in the oppression - why would they rise up?
I didn’t imply that they weren’t?
After trying to previously avoid war with US, he went and did it for no good reason. This brought second wind to the allies as Americans weapons starting pouring into the UK and the Soviet Union