How did the great men of Israel write books on how to conduct life when they differed quite fundamentally from 99% of people?

peace,
I think everyone would agree that the great men of Israel, such as the Ari, the Ramchal, Rav Kook, and the like, were people with the highest levels of intelligence, with the highest creative abilities, and so on regarding the other qualities and attributes.
So how could they write books with instructions, ways of acting, ways of living, and so on, when perhaps not even for one second of their lives did they experience the ways of thinking/abilities/behavior of a normal/average human being?
It’s like saying, for example, about people who haven’t experienced a serious mental problem like “real” depression or severe anxiety that they won’t be able to truly understand people who do experience such things.
Or for example, if the son of a billionaire who has been a billionaire his entire life were to write various books on how to act and live for people, people wouldn’t take it seriously because they would say – how can he even understand the life of an ordinary person? Let alone a poor person who has lived in poverty his entire life. Or they would read it to “gain insights” but would constantly feel that something here is not true / accurate / correct.