If Alekhine was murdered, I would think it was because he was labeled a Nazi supporter. He was virtually banned from post WW2 tournaments. His wife, about a decade older than him, was sickly and Jewish and Alekhine said he was forced to put his name on anti-Jewish statements and participate in Nazi-run chess tournaments or it would be the end for his wife.
Considering he had no problem marrying a Jewish woman, there's at least a grain of truth in Alekhine's claims.
So there's been much speculation on how Alekhine died. In his autopsy there was a large chunk of meat in his throat so he could have choked. I think it was probably some kind of disease that killed him off, maybe he got a heart attack or something like that. This smart guy on youtube gives a pretty logical argument with a bunch of evidence for this one American chessplayer dude killing him so he could win a title at a tournament. https://www.youtube.com/watch?v=xfr64zoBTAQ
So how do you think he died?