Why did Germany become republic country after World War I?

At the end of World War 1 Germany was in a terrible condition. Germany began to crumble from within. The seamen were on strike, the social situation was terrible (a lot of people were poor) and so there were many riots out on the streets (German Revolution). Germany had clearly lost the war and so Kaiser Wilhelm II was forced to abdicate. He fled to the Netherlands in exile. The moment he abdicated was the moment Germany had no monarch as head of state, and so Germany officially became a republic on the 9th of November 1918.