Speculatively, I’d say it’s social media for girls (instagram, tiktok, snapchat) and porn for boys.
However, statistically speaking, boys just don't follow male instagram models in the first place. Far fewer install instagram in the first place, and if they do, it's not to get fashion tips and lifestyle advice models. Those that do are probably going to end up very insecure too. But in practice, boys don't do that, and therefore the practical levels of harm are lower. It's just like how teenagers that have friends that binge drink end up having more alcohol related problems. It's not that the alcohol itself is more dangerous, physically speaking, the more friends that drink the teenager has. It's that if their friends are binge drinkers, chances are higher that they themselves will binge drink too.
That should be questioned too. We don't know what's causing it. It might be the parents consuming of polarizing / doomsday politics effecting their interaction with the kids. It could be parents forced to work more because of costs. It could be the after effects of Covid. It could be that therapy became normalized and kids were always this way, but it's much more accounted for because they aren't afraid to tell people about it. It could be a lot of things at the same time.