Mainly because the German people were angry at the British and the French for forcing their country into depression and economic ruin so when Hitler was rising to power some of the German people supported his new party because they thought it would help their country. Although, a lot of the Germans didn't actually support him. He only rose to power because he had the Brown Shirts (group of assassins) kill important people this terrified the rebutting citizens and if you didn't support him, he would threaten to take away your family or something to that effect. Hope this helps :)
