I don't know if there are any studies about why dark mode is so popular these days, but my guess is because of using screens on poor lit rooms or even in complete darkness.

In those conditions it's super annoying to switch from a dark UI to a bright one which I guess its why light mode gets so much irrational hate.

Obviously users should be able to choose what works best for them.

I'm in my 40s now and I care much more now about my vision. I guess most proponents of dark mode are actually much younger than me.