Why Nazism become popular in Germany …

Nazism became popular in Germany by 1930 because:
(i) Threat of communism was a contributing factor in the rise of popularity of Nazism. Though the Sparta cist uprising designed on the Bolshevik Revolution in Russia was crushed, Nazis played the card of rising menance of communism to win the support of the conservative forces.
(ii) Failure of communist party and the socialist party to put up a united front also contributed to the popularity of Nazism.
(iii) Hitler's personality played an important role. He was a good orator and his words inspired cross-section of people to support him. The working class because he promised employment and security and the propertied class because he promised to make Germany great again.

Nazism became popular in Germany due to many reasons and not one. Some of them are as follows-
A)  FAILURE OF TREATY OF VERSAILLES- Germany had lost world war I as a result of which heavy amount was imposed on them by the allies. Hitler's Nazi Party portrayed itself as a symbol of revival and tried to gain popularity among the people of Germany.
B) ECONOMIC CRISIS- After the failure of treaty of versailles, The weimar Republic did  very little to improve the economic condition of the people of the country. There was severe unemployment, poverty, market downfall, etc. Under this condition, Hitler was seen as a hope for their upliftment.
C)FEAR OF SPREAD OF COMMUNISM-Due to the fear of Russia overtaking Germany,Htlter tried to reveal to the people of Germany the negative effects of communism and encouraged them to join his party. 
All these factors combined led to the spread of Nazism in Germany by 1930s