Because power corrupts, he was able to gain control at a young age because he had the gift of persuasion in his speech and mannerisms. Once some men feel the rush of power, nothing else matters but that.

Hitler might have defined himself as an artist in his childhood but after he was rejected by the university as lacking the talent to even study art in Vienna, the rejection had a lasting impact on his life. That rejection was probably the boost that made him feel the need to prove to everyone that he was superior to others. Thus, his diabolical plan to exterminate the Jews and even Germans who he felt was beneath him.