For example, say this integration is fully accomplished. Fediverse users wouldn't have a real reason to switch to Threads, but because Threads is a much larger platform all future users are gonna go there, and not to the rest of the Fediverse. That, already, I think is an issue. Then, because it's a bigger platform, most communities are gonna start to be populated mostly by Threads users - simply because numbers rule. The 2nd E comes into play: extend. The protocols are extended. At first, it might not be enough to switch - just some quality of life changes, maybe - but the more stuff is added, the more the experience for the Threads users - aka, the majority of the users on any given community on the Fediverse - starts to diverge from the rest of the users. Now, at this point, a Fediverse user has two choices: either ignore this, or switch. Sure, many will just ignore it - the people on the Fediverse right now are the kind of people that would tend to ignore that, anyway - but plenty won't, because it's SOCIAL media. SOCIAL! If your experience differs significantly from your peers, that will bother you, and you will want to change, especially if you're in the crushing minority.

Embrace, extend, extinguish.

Hey, maybe I'm wrong! Hopefully, even. However, I do see it happening. Hope I got my point across.