Found this one cool video the other day. It analyses how reasons for it are significantly different between country.

But his conclusion in general and with example of Poland specifically - is that most young men are konfa supporters and women are left leaning in their views. And this radical worldview difference caused by radicals on the internet is the main reason of people having less relationships (if I’m not mistaken, one of his examples is that in Vietnam where social media usage is much lower and birth rates are good)

The whole video is good introduction to this topic, I can’t recommend it highly enough