I know NASCAR said the harness failed and they also changed the head restraints. But the harness might have failed because it couldn't do the forces. So you make a bigger stronger harness and the human is still scrambled eggs. The forces have to go somewhere. NASCAR has to keep up the image you know, that racing is safe, killing the stars is bad for business. They have to try and make an inherently risky business at least appear safe. But sometimes they fool people too much, for their own good.
You body is moving at car speed, and it has to be decelerated at survivable rates. And therein lies the problem that is addressed by crumple zones and material deformations. But the deceleration still must be within survivable limits -- That takes distance and area, if you want costs to remain affordable. You cannot remove costs from the equation, less no one would be able to afford the result.
People also have an aversion to "wearing their cars".
I agree with you, A carbon fiber car can survive an insane speed accident with little to no damage, the human inside however is dead, The human body can only decelerate so quickly, break that barrier and you rupture internal organs, vertebrates break as the head throws forward severing the spinal column, the brain slams into the front of the skull etc etc etc.
I was just pointing out that his particular crash may have been survivable, there seems to be some debate of him wearing or not wearing his head restraint as well. However anyone doing 50 or 60 miles an hour in a Smart Car and slams into a wall will be dead, even if there is “no intrusion into the passenger compartment” the deceleration is too quick for a human to survive the impact.