The way our social media feeds are sorted algorithmically means they're optimised to show us content we'll engage with which is often content we'll have an emotional reaction about:
Emotional reactions like outrage are strong indicators of engagement. With the most basic algorithm that sorts our feeds, this kind of divisive content will be shown first, because it captures more attention than other types of content.
this has allowed for what we might call outrage cascades — viral explosions of moral judgment and disgust. These have come to dominate our feeds and our conversations, and are becoming a prominent part of the cultural zeitgeist. source