What are the primary reason that caused Germany to lose in World War 2

I guess the answer is partly because that what he promised at the first place (work/food/more land to live/houses) was done plus... the germans were not used to march during winter time over such long distances (like the Russians were).. so it was more a question of time I guess plus partly co-incedences.

The simple answer to your question is that Hitler got far too greedy to quickly, I think mostly because the power, sucess and adulation sent him insane. If he'd have kept Japan from attacking America, gained Russia as an ally instead of trying to conquer it and invaded the other countries more by stealth, friendship and unity rather than by Blitzkrieg, he would probably have established the EU 30 years in advance of it's actual date. As the saying goes, "softly, softly catchy monkey".