Elon Musk's biographer says Musk has 'multiple' personalities — he can be 'brutal,' and also 'frightening and inspiring all at once'

• Elon Musk's biographer says Musk "is a person with multiple moods and modes and personalities."
• Walter Isaacson told The Atlantic that Musk's many personalities are "quite vivid and different." 
• Isaacson added that while Musk can be "dangerous," he can do "some pretty amazing things."

Elon Musk's biographer Walter Isaacson said he thinks the billionaire has multiple distinct "personalities" that come out in different situations.