There are literally, not exaggerating, over one billion Instagram accounts in existence. It's self-evidently not the case that they have just silently registered everybody a Threads account and are counting those numbers.
You know whats the big issue here is? That those who were nagged into trying Threads, can't back out as it would kill their Instagram accounts as well. So all those conflated numbers will be dead in the water.
You know what's irrelevant to the current conversation about how they have so many users they don't need us?
How many fediverse accounts are there total? A couple hundred thousand? And how many of those are duplicates across instances?
Whether or not all those users stick is irrelevant, the user counts for lemmy / kbin also won't have all of them stick. The point is that they do not need us or our content. They can hit a bill without even supporting activitypub.
a) building their next social network on an open platform will let antitrust regulators off their back
and/or b) a Twitter clone sounds less sexy then a web3 / decentralized fediverse play. Meta has chased every other bandwagon (metaverse, ai, etc), it's entirely possible this is just them always chasing the hot new thing so that they don't miss out. They certainly aren't going to let themselves be Blackberry and refuse to change, they'd rather desperately copy every hot new thing and change quickly to always have an offering that appeals to their customers good enough