I used to see this on Reddit, I'm disappointed this behaviour is also on Lemmy.
Users collecting mod status on multiple communities, and then using that power to mass-ban a single user from a bunch of communities.
Modlog show how incredibly trigger happy some mods can be. Minor transgressions, deserving to have their comment removed at least, but then banned from unrelated communities as a consequence. This will only get worse as users become supermods.
Edit: It seems this is how an instance ban is reported, by banning from any communities the user has participated in. Then perhaps it isn't all as bad as it seems.
In other situations, mass bans sometimes happen because it's easier. Moderators often use custom scripts they've written to ease the administration burden. Personally, I don't even provide a reason for bans, its just one more field to fill, and for the benefit of someone disruptive or acting in bad faith? Why bother.
Moderators don't owe anyone anything. If you don't like a mod, it costs you nothing to spin up another community. Hell, if you do it on another instance, you can even have the same name, and with crosspost merging apparently coming to this corner of fedi, it makes even less difference.
It's sensible to provide a reason for the bans because the community should be able to know when, why, and how you enforced the power they delegated to you. It isn't just for the one being banned.
And mods do owe the community something. At the very least: transparency, safety, fairness, and reliability.
What do you mean by, "should?" Why do you think mods owe the community something?
Do admins, who not only put effort but actual money and other personal resources into providing a server, owe something to their mods? Or do WE owe our admins?