I work in the industry at a market-maker. Jane Street is a lot more than just these two people. Prop trading firms and some quantitative hedge funds are a lot different than traditional hedge funds. Jane Street is mainly an ETF market maker, and are very good in that. They make their money because some of their core strategies work very well.

Also, JS has low attrition and traders there mostly stay long-term since it's a very trader-first place than some other places like HRT, Jump. Both SBF and Ellison had short tenures at JS.