re: OT - History Baws WW2 question

Many reasons.
1) Fear of a WWI repeat where Germany proved to be tactically superior costing heavy casualties among allies. Britain refused to back the French in the Rhineland remilitarization. British and French refusal to honor defense pact with the Sudetenland caused USSR-Nazi pact on Eastern Europe.
2) Free expansion. Rhineland, Austria, the Sudetenland, the rest of Czechoslovakia, and Poland during the Phony War and Soviet cooperation.
3) Small neutral countries were easy to swallow whole. The Netherlands, Belgium, Luxembourg, Denmark, and Norway.
4) Superior tactics with modern equipment (WWI surrender removed the "burden" of old military stocks) in the combined arms Blitzkrieg attacks knocked out France quickly.
5) Their opponents were not that much! Britain never was a Continental land power and were even less after Dunkirk. The USSR was a hollow shell after socialist mismanagement combined with Stalin's butchery. Hitler was correct when he said,"You only have to kick in the door and the whole rotten structure will come crashing down." And the massive defeats early in the Eastern invasion removed millions of soldiers, tons of equipment, and untold resources from the USSR! America had almost unlimited potential military power in 1942 but no real actual power.
6) While Germany faced a two front war, it had the advantage that it controlled the continent's resources in one centralized area.
7) The Allies also faced a two front war, but had to fight globally. America had to carry the war to Japan with British and Commonwealth help. Even the USSR had to keep some force in Siberia to keep Japan honest.

In short Germany didn't have to start playing the varsity until 1943!