Understand that world war I ended while German forces were still outside of German territory. It was a war abroad, but it wasn't like world war II where allied forces swept them to Germany. It was more like Vietnam. While historians may argue that the war was unwinnable, and it likely was, many Germans were angry at the fact that Germany surrendered at that point. Exacerbated by the fact that the terms of peace were so onerous and offensive that it left a deep scar on the German psyche.

One of the main reasons for that surrender was political and civil unrest at home, of which the communists had an outsized role in. There was even a German civil war in the aftermath of world war I in which the Communists tried to take power.

The leadership of the communist movement in Germany at this time was heavily Jewish and this led to the perception that communism and Judaism were linked.

After the German civil war, a new government was established, the Weimar Republic. This government was both horribly corrupt and ineffective. Germany sank into poverty with the onerous terms of The treaty of Versailles and Germany became a cesspit of loose morals, prostitution, and debasement. Human trafficking, crime, and poverty was the norm for a large portion of Germans, while the rich reveled in debauchery.

The Nazi party was a reaction against this.