The extreme economic circumstances of the Depression
Germany was hit with strong economic penalties after World War I -- reparations that they were to pay to the Allies who defeated them in that war. On top of that, when the Great Depression hit, it did not affect just the United States. It became a global problem. The Germany economy was in even worse shape than that in the United States. By the early 1930s, there were six million unemployed workers in Germany, an unemployment rate of more than 30%.
This situation allowed a party like the Nazis, led by Hitler, to radicalize Germany by their promises of recovering national strength and prosperity.