The most intelligent people I've know have tended to be quite lazy. The most successful were often smart, but more commonly passionate and hard working.

Most highly intelligent people spend the majority of their K-12 schooling taking classes designed for average-intelligence people who match their chronological age. They can achieve at a given level in class with much less effort than those around them, and they generally aren't given a strong incentive to achieve more. If they develop the habit of working hard to achieve at their limits, it's probably because they have a strong interest that they pursue outside of school.

I'm not saying that IQ and work ethic are linked, but rather that both are things that are to various degrees outside your control: https://www.scientificamerican.com/article/to-predict-succes.... Whether it's biological factors (e.g. there are measurable differences in the brains of violent offenders), environmental factors (lead), or nurture, by the time someone has reached the age of moral culpability, I'm not sure how much control they have over what we call "work ethic" or "self discipline."