Chernobyl showed that an accident could make an entire region unlivable indefinitely, Three Mile Island showed that an accident could happen in the US too

Nuclear accidents became real. People could no longer trust that all the safeguards and safety culture could prevent it. And the impact of how serious an accident could get outweighs the rarity.

Or a more objective and dispassionate way to look at it, is the seriousness of any potential accidents caused enough process safeguard to make nuclear power too expensive to be worthwhile