I worked at a hedge fund at the start of my career, though it was somewhat atypical as it was a very new fund and had more of a startup environment than a well established hedge fund. The work was a fantastic split between analysis and building new software to run the fund.

But to your point, the CTO of the fund was a pure math phd who got into finance/coding when his advisors asked "Ok so now how are you going to make money". which is common for most of the heavy duty quants I know.