He sat on his neck. Police procedure warns that this has the potential to asphyxiate. This was an expert testimony.
When prosecutor Steve Schleicher asked Stiger to clarify whether the risk of positional asphyxia depends on whether pressure is applied specifically to the neck, Stiger said "it's the pressure on the body" that "complicates breathing." Whether Chauvin's knee was on Floyd's neck or, as Nelson prefers to describe it, "between the shoulder blades at the base of the neck," the crucial point is that he was pressing down on Floyd throughout the encounter, which aggravated the asphyxiation risk created by forcing him to lie on his chest with his hands behind his back. That situation made Floyd's complaints that he could not breathe perfectly understandable and plausible, even if the cops thought he was faking. Exactly Where Was Derek Chauvin's Knee, and Does It Matter?
In the end, and something you keep on ignoring. Chauvin was warned... several times that Floyd was in distress. He didn't address it or didn't allow anyone else to address it.
I'm honestly quite baffled that you don't recognize that not rendering aid to someone in distress, hell increasing that distress doesn't amount to responsibility for death caused by that distress.
If I see someone else falling down on the street without breathing, not rendering aid, while at the same time preventing aid being rendered, I am responsible for that person's death. Even IF and that's not the case in this case, I'm not responsible for the fall down the street