I've noticed a few communities where the mods haven't ever contributed to the community (and its dead), or / and haven't even posted anything to lemmy in years.

Just a FYI, you can ask Lemmy World admins to takeover ownership of communities community and actively moderate it, to help revive it

It seems there were a few people who simply grabbed the community names when Lemmy grew, and had to plans to contribute to them.

Some of the communities that were affected , I've seen have a lot of potential (like some of the larger linux distros).