Read Hitler's entry in Wikipedia, especially the sections on The Reichstag Act, The Enabling Act and Dictatorship. He arrested a bunch of anti-Nazi Communist deputies and other folks in Parliament in order to have enough support to pass the Enabling Act, which gave Hitler and his party the power to pass laws without consent of the Reichstag for a certain period, which basically made him a dictator. Too many people went along with Hitler and the Nazi Party because they thought they could control him. There's a great PBS doc series called "The Rise of the Nazis". The first season is a great primer on how Hitler and the Nazis rose to power. Season 2 is on their downfall