I mean not that shocking the people living on top of another don’t belive they can live peacefully while the people they are on top of are still alive.

Its not as if there’s a lack of humans.

If they don’t want their population to collapse they can accept immigration and change their culture to be more welcoming to outsiders. Or don’t and keep on the same path.

Noone is putting a gun to politicians heads and making them do any of this. Nothing they can do will naturally increase the birthrate.