Vietnam’s campaign against corruption notched a significant victory earlier this month with the removal of a top Politburo official for “very serious mistakes and violations” while he was chair of PetroVietnam, the state-owned oil and gas company. But analysts say that there is a more complicated story behind the rare Politburo sacking—just the fourth in Vietnam’s history and the first for corruption—that involves personal and factional maneuverings at the top levels of the ruling Communist Party.

Dinh La Thang, once a rising star in Vietnam’s government, was dismissed from the 19-member Politburo, Vietnam’s top decision-making body, on May 7. Three days later, the party announced that he had also been sacked from his post as party secretary of Ho Chi Minh City, Vietnam’s largest city and commercial hub. Thang’s firing was accompanied by an unusual public censure from the party for his running of PetroVietnam, one of the country’s largest state-owned enterprises. ...