Xu Xiang, who led Zexi Investment’s ascent to the top of China’s money managers, is known in the country as "hedge fund brother No. 1" and inspired both awe and skepticism among peers for his knack of timing swings in volatile stocks. Xu, the latest target of the government’s crackdown following a $5 trillion summer stock market rout, is facing a probe for alleged insider trading and stock manipulation, according to state...