Whether it was poor planning or not, the ending sucked mountains of ass far greater than even Lucas can pull off. It was a movie with a direction to a point that didn't exist. Kinda like Matrix Reloaded, except there isn't a planned sequel.
The Nazis rose to power because Germany was economically fucked up by France. The only threat the Soviets posed was during 1941 (or so Hitler thought). I don't understand where you get your facts.