Personally I stopped using Facebook because even in the before-AI days it started becoming a glamour photo book of everyone you ever knew (and probably lots of people you only kind of sorta know), and while people certainly deserve to do and see great things, seeing it all shoved in your face every day becomes exhausting in a keeping-up-with-the-joneses kind of way.

I totally get that not everybody is like that, but I am, and so I stopped going to Facebook.

These days I'm in private Whatsapp groups for my direct family and so I learn about what they do, and not the random stuff that my neighbors and 20-years-past classmates did.

My wife is still active on Facebook and I actually do still visit occasionally to boost her posts but that's about it.

I'm a dad that stopped using facebook when I got divorced, so there's a bit of anecdata for you

I would say their priorities changed. They spent less time with social media and just did other things.

Or possibly 'men find the algorithmic/consumption based platforms relatively more appealing' and so were quicker to leave