Meta can't buy the fediverse, like Google couldn't buy XMPP. XMPP userbase was consumed regardless. My main point is that if allowed to grow into the largest or one of the largest instances, Meta has the ability to cause a lot of damage.
What can they do? They might add new features, such as custom reactions, or new types of post embeds, or something. Developers now have to choose between having broken posts, or trying to catch up Zuckerberg's nonstandards, like if it were the browser wars.
When the average user sees broken posts or can't follow their favourite people anymore because of defederation, they just have a reason to move to a better instance (Threads or some other instance that hasn't defederated). Defederation works if done early. If it's done too late, only the hardcore Meta haters will be left.
That's the worst case. Given their track record, they will use an opportunity to backstab us. I don't know what I will say if people just let Meta pull an EEE that everyone saw from a mile away. In any case, I consider Meta a massive risk for not much benefit (do we even want a wave of Meta users?).
Remember that Meta's strategy has always been to buy out or kill competitors before they grow too big. This time, when the competitor is immune to normal methods, they're all so friendly and cooperative. Why the complete 180, did they suddenly turn good?
Honestly I appreciate Apple engineers' sense of humor here