They didn’t choose a much safer version of nuclear (thorium) back when they first started building them. They instead went the tech tree route that also unlocked nuclear weapons.
Discussion
We also expect costs to go down as a technology matures, yet over the first 30ish years the costs of generating a watt of nuclear energy went up two and a half times in constant dollars. A cynic might wonder whether other energy industries may have lobbied for onerous regulations in order to limit the impact of this cheap new source.