...This is literally what happened after WWII. Hitler died, then Germany was split into East and West Germany by the two rival powers of the world, both setting each side to be sympathetic to their own.

Hitler dying in and of itself was not imperialism (not that he was directly killed by anyone other than his own hand anyways). The reorganization of Germany was imperialism. In the same way, deposing of Morgan Le Fay wasn't imperialism, but putting Jaimie Braddock of all people in her place was.