By your description of the force of impact, it sounds like the cage did a good job of absorbing the energy. Is there really a design that's practical in weight and material cost that can withstand any possible impact ? And how should it look after an incredible impact ? I wouldn't expect it to look like it did before the accident.

The bending and breaking is absorbing energy that would otherwise transfer to the driver. Had the bar broke upon a 20 mph impact, I would look to see if inferior materials were used. But at 80 mph, what would you expect ?

The design you show does appear to be a stronger way to make an X. I'm sure that at an 80 mph direct impact there would be some failure somewhere in that construction too.