The best answer is They were angry at German leaders for losing the war to the Allies.
The victorious nations of the Triple Entente in the conflicts of World War I, (1914-1918) stipulated the agreements be signed by the defeated nations. Germany, which was considered the main accused in the conflicts, was obliged to accept the impositions of the Treaty of Versailles, signed in Paris in June 1919. In general, the German state lost part of its territories and colonial domains. Despite all these restrictions, the winners imposed an astronomical indemnity on the German coffers. Germany should pay about 270 million gold marks to allied countries. Other fines were stipulated for the payment of pensions to widows, maimed and orphans. Most of these stipulations were granted to the French.
