Hitler was concerned with communism and its spread in Germany at the time. Entire towns had gone communist. The 'reds' (German: die Roten) i.e communists/Antifa were beating people in the streets, and responsible for the beating death of WW1 returning veterans. Thereafter, with the rise of the brownshirts, there were bloody street brawls between Antifa and the Nazis. When the people found out what they were in for under communism, they ran to Hitler. There were of course other factors leading to the rise of Nazism, but the spread of communism was definitely one.