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
Doesn't it mean that anyone can make a privacy respecting client, you are not forced to use the Meta client?
If as much as 10% of Instagram signs up for threads they'd be as big as twitter. Threads could gobble up a lot of the incoming population of the fediverse and once they have enough people, defederate from everyone else, limiting the available content to non-corpo instances. Defederating from threads is of paramount importance for the well being of the fediverse.
They don't need to defederate. Just extend with Theads-only features to force others to funnel into their platform or else miss content. Slowly ramp it up until the competition mostly dies out on its own.
that's not what zuck wants to do with threads tho