Let's not overlook the strategery of the Nazi leadership. They fortunately made some real boneheaded calls.
One of the most boneheaded of all calls was built-in.
Had the Germans invaded with genuine intent to liberate, a significant number of Soviets would have chosen to fight on the other side.
Deduct 2M or 4M from the Soviet side and add it to the German side.
But of course the vast majority of Soviets quickly decided, accurately, that the Nazis, at least for them, were even worse than the commies.
If the Nazis had been able to genuinely try to liberate the Russians, Ukrainians, etc. they wouldn't have been Nazis.
Boneheaded enough to make Colonel Klink look like a military genius and Sgt. Schultz look like a model enlisted man.