Revoking 230 would disrupt big sites, but would likely further cement their monopoly. Liability for user generated content means that sites that feature user generated content need to spend a lot of resources on moderation, because the consequences of a false negative are large.

People who talk about section 230 breaking up large companies seem to be harboring the assumption that section 230 will only apply to large companies. This is not the case. It will be a massive blow to any site that features user generated content. A blow that only large sites have the resources to withstand.

I think if this happens, decentralized social networks will really take off.

The "small sites" you refer to , which I'm assuming are typical forum type sites, have been dying a slow death for the past few years anyway, since FB ate their lunch.

Small sites would be absolutely devastated because the threat of being held liable for user comments will be way too large of a risk. Small networks don't have the resources to pre-moderate comments or build sophisticated automated systems of identifying high risk content. How many people would host their own site when the consequences of user-submitted illegal content being posted could mean millions in liability? Very few, if any. The result is that large players are the only ones that can survive in a market where companies are held liable for user submitted content.

Maybe if by "small" you're talking about dozens of people. But I fail to see how comparably small sites like Hacker News could continue to exist without section 230 protections. It'd probably take fundamental changes like charging users a subscription in order to pay for enough moderators to pre-moderate comments and submissions and I am unsure if that's even a viable approach.