What the heck are you talking about? Germany also lost WW1 and nobody committed genocide then neither. If you refer to the Morgenthau plan, that lost to the Marschall plan, I think history showed that the world was better of with the latter.

The main reason why Germany had so many foreign troops in the former occupation zones was simple: the Cold War. The French held the Ruhr, the British the North and the US the South. The USSR held the East. All those bases were there in case the Cold War turned hot for whatever reason, and Germany into the first ground battle field of WW3. Always better to have the troops already in theater, just in case.

Germany was left to its own devices since the 50s after WW1 and since the 20s after WW1. Before WW1, Germany didn't really exist as a nation.