He may well have thought that he was doing the right thing for Germany. He probably attacked Belgium because he knew he could win; it meant more territory and income for his country, more soldiers, more weapons, etc.That is the stupidest thing I've ever seen in my life.
How the hell do you make Hitler pitiable? If he thought he was just doing the right thing for Germany, he wouldn't have attacked Belgium and would have stayed against England and France.
However, regardless of what his intentions were, his actions were inexcusable. If he wanted to make Germany a great nation, there were other ways that didn't involve killing six million innocent people.