driver equipment to car design to track safety features
Indeed. The [voluntary, I presume] adherence to these safety features (also known as "design requirements for safety"). Have had a markedly positive human outcome. It appears to me that the "lessons learned" in aircraft design and safety may not be quite as readily being voluntary adopted into certain aircraft types. Perhaps this is a result of the right of a person to "experiment" with aircraft (or most anything else not involving explosives). Of course, the aircraft would bear warning words on the outside, informing people who might get in, that the aircraft is "experimental". I guess at the air races, the spectators also know that the participating aircraft are experimental, but perhaps they don't quite recognize the hazard of one being pointed at them.
There are references to racing cars being built to have "robust driver compartments". Some planes do too - most purpose built Ag aircraft.
I agree that structure which can dissipate a 500 MPH crash, and keep the occupant safe, is an engineering stretch, is an attempt even made? Can the canopy take a bird strike? (that is the main reason for speed limits below 10,000 feet). Military aircraft have hardened canopies, and ejection seats. But I'm sure that the air racers don't want to carry the weight. And those features won't keep a disabled aircraft out of the crowd anyway.
It's just sad that spectators suffered.....