What exactly went *right* during the Baby Boom?

The fertility discourse tends to focus on recent decline but there isn't much talk about the ONE TIME that the birth rate skyrocketed in western society: the 20 years following World War II.

If we look at the U.S. birth rate from 1800, it fell steadily for 140 years, all the way down to replacement rate during the Great Depression. And then following WWII it jumped all the way up to 3.65 births per woman.

I write more on the subject here: Why Baby Boomers are so special.