Exactly. Everybody just immediately jumps to their pet theory without actually digesting the full set of data that needs to be explained. The article very clearly lays out why those other explanations are less plausible than social media, and the cross-cultural nature of it is a big point.
All that said, the authors who publish on that site are also very pro-unsupervised free play and think its decline has caused mental health issues of its own (see Haidt's The Coddling of the American Mind).
People are really bad about interpreting complex multifactor causations, it seems in every discipline.
I think human social systems have a lot of 'anti-fragile' built into them. That is any one factor, unless it is insanely serious, isn't going to cause a mass collapse of society. We adapt and smooth things over. This is something we see in ecological systems all the time. The problems start cropping up when multiple stressors are introduced to the environment. For example, I'd say the disappearance of 'third places' forces more youth to social media thereby increasing said harm of social media.
Also, social media likely needs broken into a series of different factors on what is harmful about it. You have the direct "Kids going things to kids", but neglecting what social media is doing to their parents would be missing the forest for the trees. The 24 hour news cycle tapped into the fear sells, and online has taken it to 'fear gets eyeballs'. Add in advertisers being unscrupulous, and countless bots attempting to manipulate you, it's no wonder we're not all insane.
All that said, the authors who publish on that site are also very pro-unsupervised free play and think its decline has caused mental health issues of its own (see Haidt's The Coddling of the American Mind).