As others have said, there's a trooper/cop there already, which means an ambulance is on its way. Unless the victim/bystander ratio is less than 1:1, no need for more people to stop and muddle things up more. That just ties up more traffic and creates the potential for more collisions. Also, standing on the highway is more dangerous than people realize (well, most people). Fire trucks purposely park across lanes in front of scenes like that to act as a barrier for the responders working in the road. Adding people who don't have the awareness to stand on the side of a road is bad.
As for CPR, if they don't have a pulse and aren't breathing they need an airway so the helmet needs to come off. If that doesn't work they need chest compressions. Of course, at that point it's largely too late, but who knows - might be that one in a million. (not being callous, but traumatic cardiac arrests virtually never have a good outcome)
I'm impressed that dude tracked down the other car. no doubt the police would have caught up to him soon enough, but adding another data point to the intoxication is helpful.
