A large portion of the Fediverse is composed of people who walked away from Twitter and Reddit, who are also 800-pound gorillas. If Threads decides to play silly buggers with the ActivityPub protocol, people can walk away from that too.

The Threadiverse in particular is actually ideally suited to not care about what Meta is doing because generally speaking people don’t follow other people here (like they do on Mastodon and its ilk), they follow topics. There’s no benefit from having a single gigantic pool of users all piled into the same community, and maybe even some significant downsides.