Adam Mosseri:
Second, threads posted by me and a few members of the Threads team will be available on other fediverse platforms like Mastodon starting this week. This test is a small but meaningful step towards making Threads interoperable with other apps using ActivityPub — we’re committed to doing this so that people can find community and engage with the content most relevant to them, no matter what app they use.
Maybe it’s to avoid getting hit by antitrust sanctions and some EU legislation:
“Look, we’re open, we’re using the same ActivityPub protocol as thousands of others, our users can choose to leave whenever they want” - Meta, probably
(…then 99% of their users proceed to DGAF and stay on Threads)