What’s Behind China’s Crackdown on Its Tech Giants

China’s biggest internet companies got that way with at least tacit support from the government. Now two events have raised doubts about where those giants stand: the last-minute suspension of a stock offering by billionaire Jack Ma’s sprawling Ant Group Co. due to regulatory pressure; and the introduction of a draft antitrust policy seemingly designed to rein in the most powerful, including Alibaba Group Holding Ltd. (Ant’s major backer) and Tencent Holdings Ltd., operator of the WeChat super-a