What was one reason that totalitarian dictatorships gained power in Europe between World War 1 and World War 2?

Germany was defeated in the first world war, and were suffering from a rather bad economic depression, as their industry had been systematically dismantled after the war. With the promises of glory and power Hitler exposed he managed to convince the majority of the German people to follow him.

In Russia, the communist ideal quickly crumbled through intrigue and assassination, as the new regime was paranoid that its control over the country was tenuous and so quickly fell into political fear.