Mostly because he was a genius. Geniuses, knowing in their hearts that they have all the best ideas and all the best words and are infinitely smarter than everyone else put together, tend to listen to no one, study nothing, examine nothing and analyze nothing in depth. Why should they? They know all the best things simply because they are geniuses. It would be a waste of time to think about anything, so they just go with their gut.
Unfortunately, a jealous world tends to conspire against God-given genius and many times geniuses find the world crumbling around them through no fault of their own. Hey, it couldn’t be their fault, they’re geniuses for chrissake! But conspire it does and crumble it does and in the end the world is joyously free of another genius.
Luckily for us, Hitler himself was another such genius. More than one historian has said more than once that if Hitler had listened to his generals and allowed them to prosecute the war, that we would all be blogging in German right now. But, being the genius that he knew himself to be, Hitler went with his gut and listened to no one except maybe his astrologer. Whew!