For those of us who have no idea who this guy is and what he said, what did he do? Did he say something unapproved?
Kramnik ((ab)using his status as a former world champion) accused several other top level players to the point that one of them committed suicide.
Niemann allegedly cheated (In my personal opinion as a decently rated but certainly not elite chess player, he probably did cheat in this particular game, though proof was never given and probably never will) at a high level chess tournament and was ostracized by the chess community for a while. He has since rejoined and continues to play at a high level.
There is no evidence of suicide, and he had multiple drugs in his system when he died.
> he probably did cheat in this particular game
This is a fringe opinion at this point in time, even though it was obvious he did not cheat on day 1.
Polyintoxication is nasty because after the fact, you can't tell if someone underestimated the effects of the drugs or knew about them and used it to guarantee death.
Hans Niemann cheated in online matches when he was younger though
I have no idea why this continues to be a popular opinion among laypeople. Even at the time actual cheating experts using computer analysis determined it to be likely fair play. His accuracy was rather pedestrian, Magnus just had on off day and played terribly. There is no proposed mechanism for how he could even HAVE cheated. He has continued to perform at a similar level under much tighter security enforcement. The primary accusation seems to be that he's poor at explaining the reasoning behind his moves, but anyone who's ever watched a Hans stream can tell you that the man simply cannot speak.