What would be an acceptable outcome for you? Instances close because people stop running them, not because other larger instances exist. Ultimately people vote with their feet, so if you want to see more smaller instances they need to become more appealing than large ones.
Also not sure what you mean by seven instances under one corporation? Are you talking about cloudflare or are you saying they're all run by the same entity?
I don't like Amazon. Why do people use it? Because it's convenient, it has the stuff they're looking for, and it has that stuff at low prices. If we want people to use an alternative, we won't do it by trying to guilt them to use a more expensive and inconvenient option. To change the status quo Amazon can get hit with antitrust law and prosocial regulation, and/or a more competitive but employee/member controlled entity can be created.
That's why I like the social.coop model. Not saying it has no issues or will be around forever, but it's important for us to be able to get big while still maintaining democratic governance. A self hosted instance will never be as competitive as one with many users. The per user cost goes down the more users there are, and the network effect means more users will go towards bigger instances. So fine, let an instance get big, but let it be democratically controlled and funded.