During China’s yearslong crackdown on the tech 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 recognizable entrepreneur is back on Alibaba’s campuses – and he’s more directly involved than he’s been in half a decade, accord...