Minxin Pei is professor of government at Claremont McKenna College and a nonresident senior fellow of the German Marshall Fund of the United States. These are unnerving times for China's go-getting private entrepreneurs. The country's most flamboyant business representative, Alibaba Group Holding founder Jack Ma, has disappeared from public view after Beijing scuttled the IPO of his multibillion fintech company Ant Financial last December. The second punch landed four months later when the government imposed a record fine of $2.75 billion on Alibaba for its alleged monopolistic practices. Ma was perhaps lucky compared with ride-sharing giant Didi, which defied Beijing...