When Bob Iger officially stepped aside as CEO of The Walt Disney Co. earlier this year to hand the keys to the kingdom to Josh D’Amaro, he decided to take a cue from an Oval Office tradition. “I decided I would write my successor a letter and leave it in his desk, as we’ve heard Presidents of the United States have done recently. And I wanted it to be short. It ended up being six pages long,” Iger said in an interview published by the Harvard Business Review on Thursday. “One of the things that I did write is be aware of how much influence you have over the company. You’re inheriting a company that’s 103 years old, and you think, well,…