@Rocketman: That is exactly what the defense has shown so far: there was a large crowd that equally if not more contributed to the actions police had to take. That doesn't make the crowd responsible for his death though. They may have contributed. Same for the EMT, they arrived and couldn't get to him because of the crowd, should the EMT have pushed through, they MAY have saved him, that doesn't make them responsible. And this is the defense for Chauvin as well, he may not have died if not for the arrest, he may not have died if not for the restraint, but that doesn't make him responsible.
What the prosecution has to demonstrate is that he had premeditated killing Floyd (first degree murder), acted in a depraved manner causing his death (second degree murder) or was committing a felony causing his death (third degree murder). The first one is unlikely, because he didn't know Floyd personally, the second one is not applicable because he didn't just randomly pick Floyd out of the crowd and wrestled him to the ground, the third is unlikely because he was authorized and trained to use the force he did.
If they want him for manslaughter, that could be a thing but then they have to prove recklessness which means Chauvin knew he could potentially kill him but ignored this fact and then ended up killing him. However, as we have seen since, this was a common technique trained to him that was better than other forms of force, without his or common knowledge that this could've killed someone.
The only thing they could get him on is not following his training to the letter (and even that is unlikely) and that would neither be manslaughter or murder, but just negligence resulting in at best a reprimand, at worst, him losing his job.