“Mussolini lost the war for Hitler, he lost valuable time in launching Barbarossa in order to bail out the Italians in the Balkans.”
An often-over-looked factor. Not the only one, but without the diversion of resources, the Russian offensive could have begun when the rains stopped in mid-May. What kind of a difference would that two-three weeks have made?
Another factor is that the Russian resistance in the South was much bigger than what the German Intelligence had predicted it to be. Stalin kept huge forces in the South to repress dissent, and German Intelligence didn’t account for that, nor did they account for the speed of the Russian Mobilization in the South, which was aided by those already existing units.
That resistance, and the need to move forces South to account for it, would have a huge effect, later on, as forces neared Moscow.
I believe the Nazis should have concentrated on Moscow trying to create chaos in the Soviet leadership....Stalin was on the ropes, getting him out of the picture should have been Job One for the Nazis, who would have taken his place? I think without Stalin, the defense falls apart.