It's impossible here in any broad way. If an admin allowed it to go too far, they end up running off users, and possibly end up defederated if it gets really crazy.
There's already duplicates of half the c/s out there, particularly among the reddit copies.
You might think that power admins could be the equivalent problem, but we've already seen problematic instances be defederated widely.
Pretty much every instance out there right now that has enough users to have power mods already has specific rules against going bonkers with moderation.
It's a different system, a different culture, and the ultimate control is decentralized and distributed.
About the only people that could maybe upend that are the lemmy devs themselves, and it isn't like lemmy is impossible to fork. I couldn't do it, but there's plenty of folks that can. And, let's be real, those guys may be on the radical end of their political beliefs, but everything they've done so far points to them handling the project in a very socialist way. They could have forced the entire thing into an echo chamber instead of making it open source. They could have built in controls that would give them the ability to screw with instances remotely, but didn't.
So, nah, power mods aren't going to be a thing on lemmt any time soon. When it does happen, it'll be on single instances and rapidly handled.
That does mean we need many instances, and always be creating new ones. We should never settle on one instance. There should always be alternative versions of each sub/community/magazine, just in case power mods become insane at one of them.