Floyd went from walking around, talking, and apparently able to breathe with no problems, to dead, during the first ~5 minutes that Chauvin's knee was on his neck. Is your claim that Chauvin's actions had nothing at all to do with his death - that he simply died of an overdose by coincidence at that time, and that it would have been equally likely that he dropped dead during the five-minute period before Chauvin showed up? That would make for a hell of a coincidence.

Also, 19 ng/mL of methamphetamine isn't a therapeutically active concentration - it's not even enough to trigger a positive drug test [0]. And 11 ng/mL of fentanyl is on the low end of the range recommended for anaesthesia [1] - that same source states that "[b]lood concentrations of approximately 7 ng/ml or greater have been associated with fatalities where poly-substance use was involved," but no other substances were present at high enough concentrations to be therapeutically active. It's possible that Chauvin's actions wouldn't have killed him if he hadn't had fentanyl in his system, but that's not a defense [2].

[0] https://www.mayocliniclabs.com/test-catalog/Clinical+and+Int...

[1] https://www.emcdda.europa.eu/publications/drug-profiles/fent...

[2] https://en.wikipedia.org/wiki/Eggshell_skull