Elon Musk’s wild mood swings are legendary. His “demon mode" gets a lot of attention from biographer Walter Isaacson in a new book about Musk. WSJ’s Tim Higgins talks with Isaacson about what fuels Musk’s "demon mode" and how it plays out in his business ventures.  Further Reading and Watching: -Elon Musk’s Lessons From Hell: Five Commandments for Business  -Elon Musk Is Running Twitter on His Impulses  -The Real Story of Musk’s Twitter Takeover  Further Listening: -Elon Musk Wants to Build an Everything App  Learn more about your ad choices. Visit megaphone.fm/adchoices