George Floyd was a very strong looking man, and had been an athlete, so you wouldn't have to be Perry Mason to bring this aspect out in court, as some kind of mitigation, but as you say, so much else does not make sense so far as the action of the policeman kneeling on him for so long as shown, and repeatedly commented upon.
The actions, or inactions/failure to stop what was going on, by the other officers is more complex. One thing is for absolute certain, everyone of them, if they had their lives to live over again, would want to behave differently we can assume. I suppose you could say, elsewhere in this world, where democracy isn't well entrenched, or doesn't exist, a great many suspects must die without anyone getting to hear about it.