Germany lost primarily because of Hitler and the German way of thinking. They all thought that they were superior to the other races, which includes Russians, therefore they did not think it would be hard to defeat the Russians, that being said, I believe that the reason that Germany lost the war was b/c they spread out when they got close to Moskow, if they had not spread out and just focused on Moskow, then they could have captured the capital and who knows what could happen from there. I think that it would be a close fight if the Germans did not have to fight anyone else, but Russia has so many people that it is hard to tell.