You might be right there. I’m German. And many a man did come back later, after the war, here. A lot of refugees were forcefully relocated from what is today Poland. Also a lot of POWs came back long after the war was over. So the baby boom was a bit delayed over here.
While those facts might not be wrong in your neck of the woods, they are at least very, very US centric. That is of course ok, as we are talking about the US candidates here. But generally, keep in mind that the world is way bigger than the US. You make up a whole of 4% of the world’s population. And those numbers all vary from country to country.