Probably a crazy though, but I sometimes wonder if the pandemic/lockdowns did a number on social media activity too. Maybe a lot of people got burnt out on the whole thing after spending 2-3 years stuck inside with social media as their only way to communicate with friends and family.

That seems to be the point where most communities and social sites I'm on lost a lot of their activity/enjoyment, and where people seemed to start fading away.

Of course, increasing polarisation, an increasingly aggressive/selfish population and worries about privacy probably hit hard too.