Earlier quoted context omitted.
Pre social media, we lived in a world where information was generally separated by geography. Your comment suggests that by returning to such a state, it would result in increased radicalisation. The implication is therefore that social media has decreased radicalisation. I’m not sure I agree.
Social media has both increased and decreased radicalization at the same time. For those who already had radical ideas, who previously couldn't find others with the same ideas, they are now more radicalized (think conspiracy theories and so on). For those with open minds, it's allowed them to learn new things from people far away with very different ideas.
It can do that, but that can also backfire because the current social media platforms aren't trustworthy or transparent.
Advertising, "influencers", fake likes, bots, and all of that let small fringe groups amplify and normalize their ideas, so when open minded people come along, they see thousands of likes and hundreds of people promoting some idea, and they can get the impression it's a much more popular or common idea than it really is.
In other words, social media makes it very easy for a vocal minority to push their views on people, and it's nearly impossible for other users to discover when that's happening.