I gave examples in part 2 in my post of various routes to destroy activitypub, or nore importantly, destroy or consume the existing network of people.
Your points boil down to “Threads will be easier to use and more attractive so people will use that”, congrats, that’s the case regardless of whether or not you federate. That’s not a result of federation, that’s a result of meta having a lot of money to make good apps.
This entire argument hinges on the idea that the Fediverse is filled with great content that Meta will just steal and present to their users when quite frankly that’s just untrue. The fediverse is still a pale imitation of Reddit that is severely lacking in content and is still likely to die from never entering the virtuous cycle required to get a social network off the ground.