How to delete rogue iOS simulators and reclaim disk space?

The command used is simctl. Here is the man page:

xcrun simctl help

You’re probably headed for at least the following:

xcrun simctl delete unavailable

Related commands:

xcrun simctl list devices
xcrun simctl delete <the device UUID> 

And FWIW, Apple has an organizational boundary between user-to-user forums and user support, and the developer forums and developer support. You’re asking here on the user side of that division, and there aren’t as many developers on this side. The Xcode (developer) forum is here:

https://developer.apple.com/forums/topics/developer-tools-and-services/developer-tools-and-services-xcode

Why are they rogue?

The normal place to delete them is Xcode/settings/Components

That's me stumped then. If it were me and I didn't specifically need the version of Xcode I'd got then I'd try uninstalling Xcode then re-installing. You'll get the latest version. I don't know if you can still install older versions so do your research first if you need it.

Maybe because of the previous direct access into the directory confused or corrupted something?

There are three available, and one unavailable.

Here’s the cheat sheet I’ve been using:

https://www.testautomationstudio.com/cheat-sheet/simctl/simctl-cheatsheet/

Here’s the continuation of this thread:

https://developer.apple.com/forums/thread/817922

PS: Images make this harder, and the <> text-formatting tool here can be easier.