Answer :
Treaty of Versailles ending World War I. The end of war placed blame on Germany and left them responsible for massive amounts of war debt. The debt following World War I became so deep people could not afford food and the Germany currency became worthless. The German people easily bought into a leader who offered a group to blame (Jews) and a growth in the economy. Hitler offered a growing economy, renewed German nationalism, and a stronger military bringing Germany back to proud state.
The Treaty of Versailles forced Germany to pay back all the countries that they invaded. This put the country into a massive amount of debt. Germany's economy became unstable and many blamed the government. Constant bickering among legislators made the government increasingly weak and ineffective.