I do not agree to your premise that we can’t do anything against your scenario. It’s simply a matter of moderation or the lack thereof. Compromised Instances will sooner than later get defederated.

Best Example: lemmygrad.ml or lemmy.ml - those are the instances of the lemmy coders, which are hard auth-left, and even they got defederated by most of the fediverse, and piefed was created (besides other reasons) to get a codebase that isn’t dependent on russia-apologists.