FTA: "We find that intergenerational earnings persistence is mainly explained by differences in investments received during childhood, which in turn drive differences in cognition, years spent in education, and ultimately lifetime earnings."

So, I don't think it is as simple as your comment.

The paper is a bit more interesting than that. You can jump to the "conclusion" paragraph right at the end if you want to find out.

A few more words: Better education (better schools, more years). Better social contacts.

Genetic inheritance