Comment by hodgesrm
I think it's actually the other way around. The US Civil War predated social media by 150 years. The root causes were slavery and states rights. The result was a bloody conflict whose effects lasted for generations. That's an existence proof that existing communication mechanisms are sufficient if people really want a war.
So why is social media-based propaganda so effective today? One reason that the current polarization seems so durable is that similarly persistent root causes (such as immigration, economic dislocation, and racial attitudes) have arisen again. Blaming social media obscures the fact that attitudes have hardened. People are looking for support and social media makes it very easy to find. It seems more like a feedback loop than a root cause.
Just my $0.02. It's the sort of problem that should make us all feel pretty humble about diagnosing it easily.
Pre socials, you could attend a gathering of like minded people and come away energized and pumped about whatever the event was about, but that "high" eventually fades away as you re-entered the real world and got away from that echo chamber of an event.
Today, you can stay in the echo chamber and never hear anything other than like minded views because that's what the algo thinks you should see more of which means you never come down from that "high".
It's way worse in post-social algos than anything that's come before