Roommate killed 10+ yo cactus… Any idea what happened?

Hey, name says it all…. It was a round cactus I'd had for over 10 years, maybe 15. It sat in the same place for the last 4 years, had grow lights, I watered it every few weeks or so. Gets light ab 8 hours a day on a timer. Apparen
tly the "last few weeks" it had an issue and he didnt tell me anything.
Ive been out of town for the last 7 months and like 3 months ago I came back and it was fine. He said the last few weeks it gave up

Any idea what happened? I don't think it's recoverable at this point 🙃 wish he'd said literally anything sooner, our neighbors have over 200 cactuses and probably could have helped…..

Thanks