I've noticed that Hitler is often used as an example in the argument between the "individuals have a huge impact on history" and "history is about broad trends, individuals don't matter that much" schools of thought. Personally, I think that Hitler's life and times show that the truth is somewhere between these two extreme arguments. If Hitler had never been born or been killed in WWI, the conditions were still ripe in Germany for some sort of ultra-nationalist, revanchist movement to arise. On the other hand, if a different person led it, this political movement might have a different emphasis than Nazism in OTL. It might not focus so much on anti-semitism. It might emphasize a war of revenge against Britain or France more than a war of conquest in the east. It might be more genuinely socialist than OTL Nazi movement, or it might be more closely tied to the old military elite. Such a substitute for Hitler might be more or less likely to gain power, depending on his temperament, political philosophy, opportunism, and skill. He might also be more or less likely than Hitler to adopt a strategy that would enable Germany to come out ahead in any world war.