Good point. The trajectory of the car resulted in head-on (and "tail-on" ) contact with the ground, so the front end and back end aborbed most of the energy of the impact. If it had landed flat on the roof, I wonder if the roll cage would have held up? Certainly without it the results would have been considerably more grim.
I think if you crashed it that way 9 more times half the time he may have walked away the other half not so much. Probualy more luck of how the car absorbed the impact than anything. Crashes over 150mph cause internal organs to smack around and bleed, the cage might hold up being slammed to the ground over 200mph on the roof, but I doubt the drivers various inside organs would