I think (as their open communications on the subject have indicated) that they prefer to keep their legal liability profile slim. In the end, no matter how many users you have in your instance, you’re still alone in that court room against the monopolies that represent content rights holders.
From what I can tell they (at least the older admins and Ruud) seem to have no love for Meta, but they aren’t chicken little about it either. Federated or not, Meta can easily scrape Lemmy data, so if you mean that .world defederated to pretty up their image and make themselves attractive to Meta, I just don’t see the point, but also, it seems like a conspiracy theory to me.
There’s a piece on TF about a website that closed down years ago, and has been acquitted four times of their “crimes” of linking (as opposed to hosting), and due to a new definition of “communicate” is being sued a fifth time. The sue-happy rights holders have no compunction against going back to destroy anyone they perceive at any time to have infringed “their” works. Look at Reddit, still defending users against identification for doing what? Saying their ISP was lenient about DMCA notices. To protect against that garbage, you have to be careful, and perhaps remove content you agree with to CYA.