How can Sashi Brown, and ex-football GM, become a basketball expert? Well, truth to tell, he wasn’t really much of a football expert either. Cleveland Browns fans will remember him as a high profile “analytics” advocate, meaning that he used methods of game theory and finance in order to rebuild the Browns.
It is probably true that a mathematical mind would able to trade draft picks better than a more intuitive general manager. In many ways it is not that different from trading stocks. Brown was probably good at figuring out the relative value of draft picks, and the merits of trading up versus trading back.