Everything being legal gives my behaviour a pass. But that's beside the point.
The article does include genetics as well as nurture.
It also states that a lot of it is unknown, so we cannot be definite.
"Several studies from across the world have demonstrated that narcissism is, at least partly, genetic—in fact, according to a couple of studies, the risk of inheriting narcissism is over 50% in some cases. Narcissism, like other conditions under the behavioral genetics umbrella, is often studied using twins."
It doesn't improve my ability to gain an income so it is of little importance.
The people in his classroom were mainly wasting their time spending money on his courses while gaining little return on investment.