The fact that he himself was not a typical Aryan (blond hair, blue eyes, tall) is the strangest part about it. And it seemed that no-one noticed..

Hitler didn't get into the university of Vienna as an art student, because he was told he wasn't good enough. His interviewer was Jewish. Perhaps a reason for his hatred, but I believe he targetted the Jews, gays and disabled because he knew the Germans wanted someone to blame. The Jews held good jobs (university professors etc.) whilst the "real" Germans were living in poverty during the Depression.

This started the hate against the Jews, and with the help of Hitler Youth and the other organisations, he managed to convince an entire nation.