@ErikUden XMPP is brought up a lot as an analogy to Threads implementing ActivityPub, but I don't think it works. Google dropping XMPP support didn't destroy it, XMPP still exists today. It still had all the same users it did before Google joined the network after Google left. People don't still use XMPP today like they used to because it didn't adapt to the features people wanted in a modern chat platform. That's why we have Matrix now instead.

I think ActivityPub does have the features people want though, at least right now, and it seems very flexible to the addition of new ones.