The entire point and purpose of mastodon is to not be mainstream social media. Almost everyone there signed up because mainstream social media is so awful. The small and diffuse nature is one of the main benefits. Because it's distributed, there's an extremely niche community server for any subject you might be interested in.

Mastodon captures perfectly what twitter was at the beginning. Just people talking to each other and having fun. Not performative like fishing or whatever. No ads, algorithms, endless feeds, AI slop, or spying and tracking.

It turns out that a lot of people think mainstream social media is objectively abhorrent and want to connect with other humans in a more natural and user-driven way.

Frankly, "mainstream" is a dirty, disgusting concept here. A very large fraction of users would put a significant amout of effort to prevent that from happening. If one server did become "mainstream", as mastodon dot social did, the network treats it as a damage and routes around. Many servers just cut them off because the vast majority of attacks and spam originate from the big public servers.

Mastodon won't go mainstream because they don't want to and the system fundamentally cannot operate that way. A few individual servers may go mainstream, but we'd eventually consider it a hard fork. The network would fracture (as it has many times) and the network of small servers will go back to the obscurity we enjoy and cherish.

Case in point: Facebook tried to force their way into the fediverse network through threads or whatever it was called. There was a pretty hard split in the network as nodes that value privacy and safety cut themselves off from a literal hostile invader. Many servers went recursively through the network to cut off any servers who hadn't blocked Facebook. I haven't heard anything about Facebook trying activitypub again, so I guess the quarantine was effective.

> Many servers went recursively through the network to cut off any servers who hadn't blocked Facebook

A big problem is that this is happening with other servers as well. I've seen nodes that block all other nodes that run Pleroma because it's "for Nazis". And some of them also block nodes that don't share most of the blocklist.