And thinking any single instance can sway the entire fediverse, whether they're "leaders" or not is naive. You'd need to buy the top 100 instances at once to force any actual change in the fediverse and those top 100 were more than likely formed to avoid consolidation like that. You're worried about something that is so insanely difficult to happen and would have such a low ROI compared to Instagram and acquisitions like it. It's literally being shown that it's cheaper for a corporation to create its own. That's what Threads is.
The admin was trying to get people to understand how federation works though. Most of my interactions are on other instances. That you're even discussing another instance is the admin's whole point of how your perspective is outdated. You don't need to join populated instances. You could literally setup your own and still access other people. You can actually reach more people from an unknown instance than very large ones. Many instances ban large ones due to large ones having less moderation. If you wanted to be real insidious, a corp could create its own instance and just spread posts/upvotes/etc elsewhere on other instances. As long as they don't push too hard, it would go unnoticed.
You're entirely misunderstanding the lemmy.ml admin. Sure people might flock to large instances out of instinct, but it's misguided. The admin was trying to show that user count isn't the metric you want to look at for an instance.
What services can they offer that aren't elsewhere? If it's unique, it won't actually be that effective. It can only be scoped to the instance.
Instagram isn't a comparison because it works entirely differently. By even saying "like Instagram" belies a lack of understanding of the topic.
It's true all instances are not equal. But your extension theory is not very strong. Nor is your instance-for-sale concept. They gain nothing from buying an instance. Users don't matter. They're just as reachable as another federated instance.
Buying one instance doesn't change anything though. Instagram was the whole kit and caboodle. It made a difference. Buying one instance, even a large won't doesn't give the same leverage. Plus, it doesn't destroy competition or anything. It's not equivalent.
Your closing suggestion doesn't actually affect the process. Admins still run the joint. The admin just needs to care. Admins can even make it invite only if they wanted. Do you have any source for this marketplace of instances?
I mean, Meta can extract from the fediverse already. Having a federated instance doesn't really change that. It doesn't provide them deeper access than before. Theyre either federating due to EU policies on interoperability or trying to position themselves as the best instance in regards to the fediverse. There's a lot of clamour as to how great the fediverse is for users, now they can say "choose us, we're fediverse." Other instances need to show them the benefit of other instances and point out that they can have all the "benefits of Threads" (really just benefits of fediverse) without all the disadvantages.