They're concerned about the safety of corrupt management. Several posters here reassure that Chernobyl etc. were poorly managed and that we've learned a lot since then. But ongoing corruption doesn't instill confidence that learnings will be incorporated safely.

Saying that catastrophes have been uncommon over decades is also not reassuring as one would expect catastrophes to increase if we go from not building and decommissioning to rapid building and recommissioning.

Maybe the upper limit of atomic power catastrophe is still a low casualty count. In that case we shouldn't reassure people that we've learned and improved and instead show that even rampantly corrupt administration cannot do much harm, if that's the case.