The paint on the car was vaporized, the glass appears to have been fractured or broken away and every combustible surface was consumed.
An explosion could have blown the windows out, but there appears to be no massive buckling of body panels to suggest an explosion. IIRC gasoline assisted fires range about 1600F. That is enough to cause the windows to fracture, but the seals on the safety glass window would have failed and allowed those to fall out much sooner. Glass doesn't melt until around 2600F, so It wouldn't slag. The pictures I saw, all 4 rims were devoid of rubber. Repeating myself but, *every* combustible surface, including rubber, on the car was consumed. I do not see any evidence that a hose was ever taken to the vehicle at all.
As I worked many jobs, including that of a wrecker. As long as the car had 4 intact round rims, (it did) and I could get it in neutral, I could drag it on a rollback with a winch cable with a minimum of damage to the ground. All the ground panels were melted away. Round rims roll as well as tires, just not as fast.
Looking at that incline, I don't see any possible way you could reliably reverse up it in the dark, or why anyone would try with a suitable dirt path nearby. Before my wife and I were married, 200 years or so ago
we parked in a place just like that frequently, and we always chose the road over the side embankments.
I've seen many people concerned over the direction of the vehicle, it seems almost intuitive to me it drove up the embankment, not reversed, why would others believe otherwise?
*safety glass. Safety glass is just glass with a protective plastic layer. The plastic would melt much quicker than the glass component, but the glass would melt at the temperature glass melts. Around 2600F. The rubber seals would have melted long before the plastic layer of the safety glass.