The correct answer is: "the economic crisis, the weakness o the Weimar Republic and the provisions of the Treaty of Versalles which blamed Germany after WWI"
The weak German Weimar Republic (1918-1933) faced numerous problems, mainly economic, related to the accomplishment of the requeriments established by the Treaty of Versailles and the payment of the excessive war reparations imposed on Germany after WWI. Such impositions prevented economic recovery and stagnation led to hyperinflation. This severe economic crisis led to extremely high unemployment figures too.
Moreover, political extremism and paramilitary forces started to arise, that were intensified by the tense relationships maintained with the victorious powers of WWI, specially France and UK.
Hitler became popular by fierceley attacking the Treaty of Versailles and by promoting Pan-Germanism (nationalist ideas together with the need of the great German nation to expand its territories), anti-semitism and anti-communism, using a charismatic oratory and by constantly publishing Nazi propaganda. He pointed out international capitalism and communism to be part of a Jewish conspiracy that could not beat the Germans hence, something had to be done. In 1932 the Nazi Party obtained the largest share of votes for the constitution of the German Reichstag (Parliament),
