My guess for what you're seeing:
- The community did not have much content to begin with, and so the spam is currently overwhelming all the feeds. Info on the sorting algorithms is here: https://join-lemmy.org/docs/users/03-votes-and-ranking.html
- Controversial likely selects for content that has both up and down votes, so the heavily downvoted spam doesn't count as "controversial". I don't see controversial sort listed in the docs right now, maybe I'm looking in the wrong place
- The Mbin instance you are using likely isn't federating the content over, which can happen if no one from that instance is subscribed to it.
Not sure what's happening with Alexandrite though. That might be a bug
Best you can do is report it and wait for mods/admins to see it