Question

As is well known, there are many people who seem very smart and knowledgeable in certain fields, but are actually idiots.
For example, about Noah N. H. it says on Wikipedia —
…a full professor in the Department of History at the Hebrew University of Jerusalem. His books Sapiens: A Brief History of Humankind, Homo Deus: A Brief History of Tomorrow, and 21 Lessons for the 21st Century have been translated into more than sixty languages and have sold (as of 2019) more than 35 million copies.
And a bit further down in the entry —
Dr. Moshe Rat wrote that “unfortunately, examining his books reveals that the aura attached to the man is very far from justified. His books and articles… are full of flaws, errors, self-contradictions, and an embarrassing lack of understanding of many of the subjects he writes about,” and that “Harari’s article (regarding the marginal contribution of Judaism to humanity) suffers from flaws throughout.” About this article, Michael Abraham wrote that “…so much nonsense, demagoguery, begging the question, and unsupported assumptions, in one article. It’s gibberish that is even more concentrated than in his books.”
In various answers of yours, you write about different “great figures” that they are at a low level of thinking, and so on and so on.
I want to study different fields, including in the world of Torah, and I know from my high-school years that I have potential (gifted class, top-level matriculation units in a lot of subjects, etc.), but I’d rather have the simplest job than be a professor / great rabbi and be an idiot without even being aware of it.
So how can a person actually know…? Noah L. H., presumably, is sure he’s a great genius, and so are many, many other people in the sciences, in Torah study, and in other areas too (for example security, where a lot of “experts” who really studied the subject and have decades of experience in the field seem to me to have far worse judgment than many five-year-old children — for example, that it makes no sense to release a thousand-and-some terrorists for one captive, and yet many “security experts” supported it).
And what exactly is the difference between someone who is smart and genuinely smart, and someone who isn’t? Is it something in the personality? In the learning style? How can I “diagnose” in myself which type I belong to, and “diagnose” whether I’ll be the type who is an idiot without knowing he’s an idiot?
I understand that this is a question that maybe doesn’t really have a perfect answer, because if it did then everyone would do it. But even if there isn’t some “one perfect answer,” what answers do exist? What can a person do / what should one watch out for / how can I do the maximum to make sure I’m not on the wrong track?
Thanks!