Links to source articles below.
Yesterday 30 million users signed up for threads, which is already more than active users in the fediverse.
Furthermore, it seems that Meta hasn't launched threads in the EU due to uncertainty regarding the Digital Markets Act. It is entirely possible that their intent to federate with other Activitypub instances is entirely a cheap way to avoid being labeled a gatekeeper and avoid other regulatory requirements or restrictions.
It's future use of ActivityPub to get better publicity or scrape a bit more data might be an added benefit but not it's true purpose.
We'll see if launch in the EU goes hand in hand with them turning on Federation. I suspect that ActivityPub and the Fediverse are merely an afterthought to them and a convenient way to avoid being impacted by certain regulations.
Edit: Found a brief overview of the DMA. Among other things they say:
"The DMA aims to ensure the interoperability of messaging services allowing users on services like WhatsApp to send messages to users on smaller services like Signal"
https://ec.europa.eu/commission/presscorner/detail/en/ip_22_6423
Exactly, due to metas nearly unlimited funding they can afford extra server strain for exclusive features that you'll miss out unless you're on threads
I don't know if I'd feel like I'd be missing out on anything personally, I don’t have any interest in what people from Facebook or Instagram have to say as I feel like it's going to be pretty watered down interactions with little thought behind it.
If they remove themselves from the fediverse equation after amassing a following, I would hope we would be left with what we just have here at the moment, which I'm quite happy with.