Nigeria’s $20 billion Dangote refinery—the mega-project meant to free Africa’s top oil producer from decades of fuel imports—has been hit by “repeated acts of sabotage,” according to billionaire owner Aliko Dangote. The company says it has already fired workers and reorganized staff to stop the incidents. But behind the dramatic claim lies a bigger question: is this really sabotage, or the first crack in Nigeria’s most ambitious industrial gamble, one that was supposed to rescue the country from its ruinous…