I was surprised that the marshalls had open face helmets. I wouldn't want to be diving into a fireball like that to help without decent protection If he had been unable to get out on his own for any reason I don't think they could have helped much.
I also wonder if the car breaking in half actually helped as it meant that the fuel cell wasn't in the part that caught fire. An extra 100kg+ of fuel in those flames & I think it would have been a different result.
I just think he was amazingly lucky to walk away from that and was very surprised to see it - along with the TV directors etc as they immediately cut away.