Even though it took me way too long to get onto here I wouldn't be too worried. In my layman's opinion nostr just needs more niche groups to realize it's a worthwhile protocol to use. Mastodon and activity pub were extremely niche for a long time, it took Elon taking over twitter to start the massive shift. I foresee something stupid happening with activity pub (specifically mastodon doing something) then more people will either join here or bluesky.

Also AP servers do have something that nostr kind of doesn't: A sense of community with federated servers, and users on your own server. Personally that never bothered me I only used single user instances, but I imagine that a lot of people like having that.

IDK. Kind of rambling here, but my final note is that I think the best part of nostr has to be the private key / public key authentication. I dream of more services doing this it's just such a based way to handle accounts. That concept might be another barrier though for some users.