Why did the Nazi Party gain popularity in Germany after WWII?

Germany had suffered heavy losses during the war, both in lives and industrial power. 6.9 to 7.5 million Germans had been killed, roughly 8.26 to 8.86% of the population (see also World War II casualties). ... As a result, the population density grew in the "new" Germany that remained after the dismemberment.

You mean by WWI, so basically after WW1, the Germans lost and they were angry then the Great Depression came. After the Great Depression started, a guy name Adolf Hitler rose to power by promising the Germans revenge and Germany to be the greatest country in the world. So people believed him and that's how the Nazi party gain popularity

Explanation:

paper money known as continental currency, or continentals.