My theory is that social media simply increases the connectivity and reach (of the “rumour mill” or what have you) and thus it amplifies an existing social “failure mode”.
(That and earlier mass media was heavily moderated and regulated, while things like Facebook or twitter/X are basically a free-for-all).
Facebook/etc aren't a free-for-all, they're much worse than that - they selectively provide a stream of news designed to drive "engagement", of which angry obsession is one type. Social media aren't "platforms", they're content distributors (despite the industry's own efforts to establish use of the term "platform", which sounds far more neutral).
(That and earlier mass media was heavily moderated and regulated, while things like Facebook or twitter/X are basically a free-for-all).