He died of cardiac arrest IIRC. Did holding him down assist in expediting the death? Possibly but it's not the sole reason for his death. Most definitely it was not the color of his skin.
Want proof? The numbers don't lie. Look them up. White vs black killed by cops
Doesn't matter whether he took a lethal dose or not because even if he was overdosing and about to die, Chauvin's knee accelerated Floyd's death by raising his heartrate and restricting blood and oxygen flow.