"In this case who's fault is it? The drivers , tesla or the safety board for allowing autopilots to be sold?"

Obviously the insurance. In Europe you need to have insurance to pay whenever is your fault.

With autopilot the only difference will be that the event of having an accident will be less probable. This means that paying the normal driver fee the insurance company will be making money if you autodrive.

But most of the time the fault will be on the other side, because the autopilot is not going to drive like a drunk or slept person. It will be deer or dogs or children on the road when they should not be there.