Answer:
The treaty of Versailles.
Step-by-step explanation:
Germany was also one of the main perpetrators in world war 1 that ended in 1918. As a punishment for their action, the Allied forced Germany to sign the Treaty of Versailles. This treaty basically an agreement that forced German to pay off all the economic damages that occurred during the war.
The amount of debt was too hard for Germany to handle. It caused a huge economic depression in the country, leading to mass poverty and hunger that made the people lost their faith to their government. This what's causing the collapse of their government in 1920's and 1930's