You don’t need the friends, that is just one example. You have to think of the general concept and logic; Lemmy, as well as kbin, have communities. If one place manages to secure all or most major communities, they can pull the same thing. And Threads is meant to be a Twitter replacement, so you do have the bit about connections, as well as influencers. It’s like Mastodon, but completely centralized.

So the same logic applies: if Threads joins the Fediverse and most people go to Threads, then most users who are not on Threads will still end up having a lot of discussions on Threads and following a lot of people there. Then some day, once Threads gets big enough, it will stop federating and Fediverse users will be forced to move if they want to keep those connections. Meanwhile, Mastodon dies. Lemmy and kbin might survive because they fill a different niche; however, if instances start federating with Threads and making it possible to follow people on there, then the same exodus will happen.

We can learn from history, or we can let it repeat itself. Federating with Threads would mean a huge failure to learn from history. And then maybe ten years later you’ll be the one trying to warn someone else as they tell you how that time it’s totally different.