As Boeing’s latest chief executive, Kelly Ortberg’s job was never going to be easy. On Wednesday, it got harder still. That morning, Ortberg had faced investors for the first time, telling them that ending a debilitating strike by Boeing’s largest union was the first step to stabilizing the plane maker’s business. But as the day wore on, it became clear that nearly two-thirds of the union members who voted on the company’s latest contract offer had rejected it.