The bit that they stole it is sarcasm. The bit that Afrikaners have the most collective wealth in ZA is just facts:
https://en.wikipedia.org/wiki/List_of_South_African_billionaires_by_net_worth
The top 4 richest people in ZA are all Afrikaners, the next 16 most richest together still have less wealth than the top 4. Then throw in the Afrikaner millionaires and high powered CEO's and yes, not to perpetuate the BS that they've built success on apartheid, but the bulk of ZA wealth still sits in Afrikaner hands.
EDIT: sorry, Oppenheimer doesn't really count I guess, I'd bet he's fluent in die taal though