Re: dentists. I have a few friends who are MD's who say they went into it to "help people," and that if they "just wanted to make money," they would have been "one of those tech CEO's." But when you look at how they run their offices and finances, you see that there is very little crossover between their medical skill into business. They just assume that they would be a successful CEO.
I've noticed it as a pretty widespread phenomenon for anyone who has the subjective experience of being competent and thinking that's enough to translate to other fields.
Super common in hot takes on politics, medical contrarianism, etc.
Though it's probably true that certain fields are more predisposed to it than others.
But it definitely does seem to be especially pronounced with engineers.
(NB. I am a software engineer, and not a sociologist, so, argh, this is potentially getting a bit meta.)