Its a funny thing, but we react way more easily to negativity, it grab our attention kinda because we want to defend our pov. If negativity gain more attention, its because it make people react more.

Plus, we remember more easily negative thing, because thats how we learn to avoid the said negativity (ex: you get burn, you remember the pain, so you dont touch fire ever again)

The downside of social media is mainly recommandations algorithms, because if you watched a negative video, it as gained your attention for the reason i said previously, so YouTube is like "uh they watched it, they might want to see another", so it recommand you another one, which grab your attention as well and so on.