Why was the German army kept after the first world war?

After the First World War, the Paris Peace Conference took place, at which the United States of America decided to keep the German army in order to counter the rapidly developing England, France and the Soviet Union, and also because Western Europe considered the Bolshevik system of Russia more dangerous for the peaceful life of the continent …
Thus, in the event of an attack by the Soviet Union or the start of Bolshevik activity in the European part of the continent, they could be contained by the German army.