Since Elon Musk took over Twitter last month, his stewardship of the social network has been marked by turmoil, intrigue and no shortage of questions. Here’s one: How much time is he spending on his job as chief executive of Tesla, the electric-car maker?Robyn Denholm, Tesla’s chairwoman, testified in court last week that although she did not know the answer, she was not perturbed. “The quantum of time isn’t a measure that concerns me,” she said. “It’s more the results that he’s able to drive.”But as Mr. Musk has become consumed with Twitter, Tesla is facing a range of threats to its business and its stock price has been plunging. Some corporate governance experts say Tesla’s board needs to e …
