Monopoly power seems secondary here, with the real problem being that there are sufficiently many people now with a totalitarian impulse to forbid others from engaging in speech they dislike that overrides almost any other principle, and no equally obstinate opposition. I am not engaged in and have no interest in any KF-like activity, but merely wanting to choose an ISP, domain registrar, Mastodon instance or email provider that would not filter them as a matter of principle would expose me to the risk of becoming collateral damage, as the armchair censors pressure the closest amenable nodes to participate in what they see as "cutting out the rot" - excise DNS records, range-ban, defederate from your node and recursively any node that would not participate in defederating you, thus forcing the whole world to pick a side.