We know AP can be tricked relatively easily to operate without a a hand on the wheel and without an occupant in the driver seat. The remaining questions were how AP could have operated on this residential road, and how it could have reached a sufficient speed over such a relatively short distance to have caused a deadly crash.
Well, I think this video resolves those issues....
Musk says there are no records of the AP being engaged, but that could very easily be a simple matter of the crash occurring and disabling the modem before it could send the data to Tesla servers.
So really the only important unknown at this point is the state of the seatbelts found at the crash site. IF the driver seatbelt was found at the crash site to be engaged, that essentially PROVES that these gentlemen were using the car in a very stupid manner. And we now have pretty good evidence to indicate that the simplest explanation is that AP (and these men’s stupid use thereof) caused this crash.
Said another way, we now know that it was possible for AP to cause the crash, so this is the simplest explanation IF the driver seatbelt is shown to have been engaged at the crash site.