Isn't it his mother who raised him? Elon Musk also left South Africa to start in the USA, where he succeeded.

I guess: genetics + parenting > rich people background

Also, i think there is one generation in between poor and rich.

This is as fast as it goes:

1st generation: Poor

2nd generation: wealthy (mostly through entrepeneurial or hard work) where they explore investments. Mostly started a SMB or choose a profession with a lucrative income.

3rd generation: extremely rich: good investment decisions or a 0,01% company ( worth 100 million's).

Getting from 1 to 3 in one step is almost impossible. You need the stablility from the 2nd generation to get to the 3rd ( getting investment loans, contacts, ...) and the opportunity to "hit for the stars" multiple times.