Safety changed the racing
Improved survivability did not only save lives; it altered competition. Moves that would once have been unthinkable became normal, because the consequence of a mistake changed. That is worth stating plainly, since the racing people now enjoy is partly a product of engineering they never see.
Method over instinct
The gains came from unglamorous work: recording incidents, analysing loads, testing barriers, mandating equipment that drivers initially disliked. Almost none of it was intuitive, and much of it was resisted. The lesson is that safety improves through investigation, not through the confidence of experienced people.
The risk of forgetting
The danger now is the assumption that the problem is solved. Every generation of cars introduces new failure modes, and each series has to keep re-earning its safety record. Treating the current standard as permanent is the one attitude the history of this sport most clearly warns against.