A Jane Street trader's risk tolerance does not equal Jane Street as a whole's risk tolerance. When you have 1,000 traders, each individual trader's risk profile can be much higher. There are also guardrails around compliance, risk management, etc. at the firm level that traders aren't necessarily involved in.

The things that made them great traders also made them much riskier choices to lead a larger company. To them, compliance is an obstacle in the way of profitable trades.