I disagree, the monster always existed. There is a reason "If it bleeds, it leads" was a saying long before social media existed. Also, "A lie is half way around the world before the truth puts its pants on". These are default human behaviors that have always existed. In the past there were particular global limits on the spread of these behaviors base on things like "A horse only goes so fast", or there are a limited number of telegraph lines or radio stations.

Controversial, hateful stuff was always going to rise to the top. The difference between now and then is we have pretty much unlimited bandwidth covering the globe to spread the message. If you made FB disappear you're going to see the exact same behavior in mastadon servers, just hoping the scale is limited by lower audience sizes.