I wonder if Fediverse, Blue Sky, etc will catch, or if it'll end up in the same boat. Threads too (yes it's backed by Meta, but G+ had Google behind it ...)
There would be pain if mastodon.social failed with zero notice. People would lose access to their accounts and would need to find a new server where they'd be starting over. Some may have backed up their contacts, but most wouldn't. If mastodon.social gave a couple months notice, people could migrate to other servers. given that mastodon.social is the largest server, there would be some growing pains as other servers worked to accommodate new users, but it's possible for the Fediverse to continue.
Note, I'm not saying that the Fediverse will be incredibly popular. I'm simply noting that there's an amount of resilience. Once Ello's owners ran out of interest or money, that was the end of Ello. Even if others had a huge interest in seeing it continue, there was nothing they could do. Even if the Fediverse doesn't "catch" by your definition of catching on, it has caught on for enough people who have moved there and will remain there.
That's why I feel happier in the Fediverse. It feels like something the community controls. Sure, I don't run my own server, but I possibly could in the future and there are enough people running servers that I don't feel beholden to any one entity. It just feels like something that can stick around - even if the cool kids aren't interested. Enough of us like it and we'll keep it going even if some of us become disinterested in it.