Going back to the scene of the incident, we know that one can plainly see that Floyd was apparently on drug's or had them in his system as he complained constantly (as he attempted to resist), that he couldn't breathe.
It was evident that he was having some sort of panic attack that usually is associated with being on drug's or rather it's highly possible that he had consumed drug's in an attempt to get rid of them before being arrested maybe. It's possible that he had a heart condition from doing harsh drugs or maybe it was just hereditary over the span of his life time. only for it to catch up with him in the form of a heart attack later on down the road.
What Chauvin did may have looked bad, but it didn't cause Floyd to die as many don't think. Any healthy criminal could have withstood the restraint method that Chauvin used in order to get compliance in the situation.