During China’s years-long crackdown on the technology sector, Alibaba Group Holding Ltd.’s internal messaging boards lit up with dreams to “MAGA”—Make Alibaba Great Again. Now, the company is deploying one of its most potent weapons to accomplish that mission: Jack Ma. After vanishing from the public eye at the outset of an antitrust investigation in late 2020, China’s most recognisable entrepreneur is back on Alibaba’s campuses—and he is more directly involved than he has been in half a decade, according to people familiar with the company. Signs of his unseen hand are coming into sharper focus, perhaps no more so than in its pivot to artificial intelligence and its declaration of war on e-commerce foes JD.com Inc. and Meituan. Ma was instrumental in Alibaba’s decision to spend as much as 50 billion yuan ($7 billion) on subsidies to beat back JD’s surprise entry to the market, said one of the people, requesting not to be named because the matter is private.