When a company uses Embrace Extend Extinguish, they are relying on network effects to drive people to their side. So let's say Threads comes out, starts federating, has a big established userbase, and then they come out with some new, proprietary killer feature. It could be great moderation tools - something kbin and the fediverse need, no doubt about it - but whatever the feature is, it draws users away from the existing fediverse infrastructure and into Threads. Threads then makes massive changes to the ActivityPub spec, building the walled garden back up again. Only this time, they've actually siphoned off some of the users you originally had in the community. The result isn't the status quo, Meta peeled away users who otherwise would have stayed.

By the way, while a "small community of tech nerds" is perfectly fine in its own right, I would argue the fediverse has already grown beyond that community. They're a large contingent no doubt, but there's also law enthusiasts, news outlets, game developers, users from Germany, Japan, France, Finland, and I follow them all. To see them leave for Threads would be a shame.