I agree that he did not murder Floyd. The autopsy showed that Floyd had a more than lethal dose of fentanyl in his system which, had there been no police on the scene, probably would have killed him. Afraid of being busted, Genius Lifetime Criminal Floyd probably ate the last two hits of fentanyl just before he got arrested.
That takes a Genius IQ, to eat a lethal OD of fentanyl, rather than to leave it in his pocket and get busted for it.

Nevertheless, Chauvin screwed up. The big guy was handcuffed behind his back! What threat did he pose? Chauvin should have turned the guy loose and gone over to Plan B.