Bob,
You mention ' Hitler's insanity'.
Far from it.
It made pefect military sense to attack the USSR in Operation Barbarossa. Starting in the early 1930's, a little known fact is, to circumvent the provisions of post WW1 treaties, Germany had military factories inside the USSR, developing new tanks, aircraft etc. But within these factories, open to Russian view, where secret development facilities, unbeknown to the Russians, developing what the Germans wanted to hide from the Allied powers. Ontop of that, the German Abwehr succeded where Stalin had failed. German Intelligence mananged to convince Stalin as early as 1934 to shoot his most competant of the Officer Corps, using disinformation as to their loyalties.
This left the Russian Army basically 'headless' until Stalin was persuaded by what was left of his Generals to begin radically rebuilding his army in 1938. Hitler could not allow this to succeed and thus , having bought 6 years of peace on his eastern front, in which he invaded and occupied most of Western Europe, he had no option but to invade.
The only thing old Adolf did wrong, was to invade in june and not march.
If he had launched the operation some two months earlier, chances are, he would have captured Moscow before the winter closed in.... and all that would have followed... Thank God he didn't.