Because "safety regulations are written in blood". Disaster happens, reactive preventative measures help keep the disaster from reoccurring in that specific manner.

...in fields governed by science and stricture, anyway, like nuclear power or aviation.

Much like cybersecurity, the safety of nuclear at this point pretty much comes down to people, and whether or not they choose to invest in the best practices or if they get too lax. Right after a nuclear accident, the math suddenly looks different to the bureaucrats and investing in safe, reliable operation suddenly becomes worth it again.

It's the same after any accident. presumably lessons have been learned, procedures improved and people more vigilant.

The valuations will be cheap, but they will have gained extremely valuable insights that will hopefully lead to new and better designs? Personally, I think there is more likely to be a period of culls and bankruptcies.

They will be less likely to compromise on safety to cut costs?