Maybe I’m not getting something here, but neither Mastodon nor Lemmy are private, you can find everything open for everyone already, so how would federation change something there? Federation doesn’t mean everyone would use their app, so they wouldn’t gain any app usage analytics.
Also I don’t get how your metaphor make sense. The amount of fediverse users is a rounding error next to threads, instagram, WhatsApp and facebook. So there’s not a "lot a tiny things that can add up", only a small amount of tiny things which don’t really add up to anything.
Sry, I‘m still not following. I don’t understand your argument, are you saying they want to federate to gain additional users to grab data from? Because I don’t think that’s going to be a significant amount of people.
Most people don’t care about what makes the fediverse desirable to its current users, all it does is add friction to them and therefore I don’t see it growing much either.
I think the reason why meta wants to federate is this:
I don’t think they’re doing it to "get more data" or to "take over the fediverse". There’s nothing worth taking over and they can probably get the data anyways, it’s all openly available. So it’s basically all upside and no downside for them.