It’s been a while since I read about it, but iirc Chernobyl is suspected to have been sabotage because they turned all the safeties off and then basically walked away until it started melting down.
Fukushima was doomed from the start. Iirc they were told not to build the plant there due to extreme earthquake and tsunami risk, but they did it anyway.
Those two disasters were caused by stupidity and negligence. You can argue that humans can’t be trusted with radioactive materials, but the process itself is pretty safe. Meanwhile coal plants release significantly more radiation over their lifetimes than nuclear reactors do.