I'm fairly convinced that this is Zuckerberg's plan to subsume #Mastodon.
https://www.theverge.com/2023/12/13/24000120/threads-meta-activitypub-test-mastodon
@kel That's possible, but it's also possible that they could see benefits to extending their (users') reach into other platforms without taking over.
Threads is meeting user needs better than many other platforms, yet if it (or rather Meta) took over Mastodon, there would be a revolt from the people who left corporate control (X-Twitter) to go there.