Why did the US put their money behind the rebirth of a country rather than completely erasing the past of it after WWII?

The US put their money behind Japan and Germany for their rebirth after WWII. They were both devastated with the loss of war and most of their cities were destroyed, but why did the US want to completely erase their past and put them completely on a path of democracy, rather than just a country that did not align with Soviet interests?#####Edit: Sorry for the mistake, it is r/AskTeenGirls and I don't want to get in trouble with mods. I'll wait an hour and then I'll delete this post.