In most instances (like beehaw) it's really just because lack of good moderation tools at the moment is making it difficult for them to handle a large influx of users and it's intended to be temporary.

Personally, I think defederating is overkill, but I'm not an admin and I empathize with the difficulty I'm sure they're facing with such a rapid scale up. The best way for most people to help this situation is to just do a good job of properly upvoting & (if enabled) downvoting content to help naturally sort content, and help report when you see people acting against the rules of a community to help it's mods.

People who are technically savvy could especially help by participating in the development of FOSS Lemmy mod tools.