Degree success is not proven to be causative as opposed to a correlation. You get even stronger correlation to income from the colleges you apply to rather than graduate.
I strongly suggest that this is due to being colleges that you can afford if you get in which directly correlates to your parents' incomes, connections, and support which greatly increases your odds to becoming a richer adult.
Parental socioeconomic status has a greater correlation than income, and IQ has a greater correlation than that. If your parents are Syrian refugee doctors in Germany you’re going to do better than the average German even if your family arrived with no money and not speaking German. If you’re an American with two parents with JDs working as public defenders you’re not going to grow up rich bit the chances of ever being poor are quite slim.
