To be fair, you don’t have to be stupid to be clueless. We’re all clueless about plenty of things.
I mean, if you actually think there's a pool of "lava" that's dangerously radioactive at the surface, while people are walking right next to it, you might be a bit "stoopid". The whole reason water is used is that it shields from radioactivity pretty well
Why would the average person know this about the water used in nuclear reactors?
There are also plenty of jobs where people are in close proximity to insanely hot/dangerous liquids.
That's exactly my point, people are clueless about the basics of nuclear power. Why would they know it? I mean, why would the average person know what a linear equation is or what year the first world war started?