I assigned you as the moderator to [email protected]
Assigning/removing mods is a manual process handled on a case-by-case basis. There is no official policy about removing banned users from their mod roles, though that doesn't seem unreasonable.
Communities with no mods (or absent/inattentive mods) keep humming along until something brings them to the admin team's attention. There are hundreds of communities like that on this instance. Lemmy.world does have a Community Team who try to find and address communities that need moderation help. It's a big task, though.