When the head of a large state-owned Chinese insurance company was recently asked at a meeting about one of his biggest private-sector competitors, Anbang, he shook his head in frustration. “We don’t understand their business model and keep losing market share to them,” the executive said, according to a person present. This week officials from the Chinese Communist party’s corruption watchdog are combing through Anbang’s books to answer such mysteries after detaining the group’s chairman, Wu Xiaohui, on June 9, according to two people familiar with the investigation. The dramatic developments at Anbang’s Beijing headquarters tower this week represent the culmination of two longer-running narratives: a financial sector investigation into companies that regulators fear are using dangerous amounts of leverage to fuel their businesses; and stricter vetting of outbound mergers and acquisitions since late last year in an attempt to stem capital flight. In recent years Anbang has emerged as one of China’s most acquisitive companies. Since October 2014 it has made more than a dozen deal