Risks had not been factored in as likely (like in Japan the authorities have demanded protection against earth quakes and tsunamis, but only to a certain level

Risks had not been factored in as likely (like in Japan the authorities have demanded protection against earth quakes and tsunamis, but only to a certain level and they were surprised to learn that over the lifetime of these plans stronger events happen than anticipated) and if anything happens, the companies are simply not insured - other than via the government, which had created the demand and the environment for these reactors. The companies are also not well prepared if larger accidents happen. Example: Many old reactors never were designed to withstand an impact of a large passenger airplane. Large passenger airplanes don't fly into buildings. Right? Well, we have learned in the meantime that this scenario is not that unlikely, since 9/11 and for example the Lufthansa/Germanwings pilot, which flew an Airbus into the ground in France killing all passengers on board. https://en.wikipedia.org/wiki/Germanwings_Flight_9525 https://en.wikipedia.org/wiki/Germanwings_Flight_9525 One could now just let these old reactors run. What to do with the risk? Well, set up military systems to shoot down aircrafts approaching a reactor site? Adding more concrete as a protection? I'd guess that there were some clever people exploring the options and in the end its just to costly to do something working...