Earlier quoted context omitted.
Only because we believe, because of the movies, that largescale event SHOULD behave as if orchestrated by a logical, sane author. History is just, all of us, doing things selfishly.
That is actually why Hitler had an incursion in the USSR while waging war in North Africa and the Atlantic, creating an anti-Hitler coalition and thus having no chance of an outcome that isn't a catastrophe for Germany. Surely an unwise decision. The Soviets knew in advance of the invasion of the USSR but Stalin could not believe that the Germany could do such thing. Not because he trusted Hitler, but because such a…
If Hitler hadn't been a deranged fool he would have not sent the SS into Czechoslovakia (which turned the initially rejoicing population hostile), and would have immediately drove right for Moscow. Had he done that the Russians would have had no communication lines, which would have made it massively harder for them to organize a resistance.
Hitler in some sense was the best friend the Allied forces had. Every time he made a major military decision (eg "let the English rescue all of their troops at Dunkirk") it turned out to be really stupid. And the conduct of the Russian war shows lots of examples of that.