MontyB
These are all good reasons, and some either led to, or are subcategories of the major reasons which were
- failure to have any real plan to invade Britain and clean up the west before attacking Russia thus ensuring a 2 front war.
- failure to place the economy on a full war footing until it was too late
From both reasons this follows:
They were simply out numbered, out gunned and out classed once both Russia and the USA were at full war footing.
It is also noteworthy that Germany didn't make full use of their female population for idealogical reasons until it was too late.
In addition to 1) and 2) above may I suggest two other reasons
3 Subjugation and terrorisation rather than placation and utilisation of the population of conquered territories in the East who must have surely have more reasons to hate Stalin than Hitler initially.
4 Failure to coordinate strategy and amalgamate resources with Japan. Japan's navy together with the German U boats would have been more than enough to eliminate the Royal and Merchant Navy in the Atlantic, bringing a swift close to the Western front and prevention of a US foothold in Europe. Moreover, the mere possibility of a Japanese attack from Manchuria could of avoided the Russian 41 winter offensive that started the rot.