Because socialists failed to stop the senseless massacre that was WWI. I don't know if "willing" is the right word, but nationalist propaganda certainly triumph

Because socialists failed to stop the senseless massacre that was WWI. I don't know if "willing" is the right word, but nationalist propaganda certainly triumphed over international solidarity among the working class, sadly. The rise of the Nazi party in Weimar Germany was a direct consequence of the punitive nature of the Treaty of Versailles.