Let's see:
1) the US contemplated using its mythical superweapon (a) against the Russians after WWII, (b) against the Chinese and North Koreans during the Korean war. By the time the Vietnam war was going badly, the Russians and Chinese had their own superweapons.
2) The Germans allied with the Russians with betrayal in mind.
3) When the Germans attacked the Russians, they didn't have a second front (unless you consider North Africa a second front). There had been an abortive landing at Dieppe, which if anything had bolstered German confidence that their western front was secure. Bear in mind that the US had not entered the war and England's collapse seemed inevitable (and if Rommel had taken the Suez that would have been it for Britain).
4) Every one of Hitler's major offensives had been thought insane by Hitler's own high command (e.g. the British and French outnumbered the Germans in both men and tanks at the outset of the invasion of France), so their very reasonable objections to the Barbarossa campaign fell on deaf ears. Is there anything more plausible than hubris?
My favorite example of implausible actions in WWII was Hitler's declaration of war on the US after it declared war on Japan. That never made sense to me until I read A World At Arms -- a history of WWII that emphasizes politics, diplomacy, and intelligence over battles. The Germans relied desperately on Japan for rubber (even synthetic rubber required a certain amount of real rubber as an ingredient). A fleet of u-boats was dedicated to transporting rubber from Japan to Germany, and Germany needed Japan on side or it was in deep trouble (fighting the Russians with no rubber).