In this article in the Wall Street Journal, Phred Dvorak writes about the difference between the CEO position and the COO position. Dvorak writes, "CEOs not only perform different tasks from their second-in-commands -- who typically focus on running operations -- but they have to act differently, too. That means the two roles often demand very different personality traits, say people who have been there." He goes on to quote a number of executives who argue that some folks have the personality traits required to be a highly successful COO, but they don't have the attributes necessary to thrive as the CEO.
I will acknowledge that some second-in-commands are not well-suited for the top job. However, I think it's rather simplistic to argue that the two jobs require fundamentally different personality traits. After all, most successful CEOs did spend time as a second-in-command prior to taking the top job. I think it's more important to think about the skills, activities, and behaviors that differ between the two roles. Then those who aspire to these roles must think about how they must CHANGE their behavior to thrive in each role. Perhaps it may require some development or coaching to adjust to the new role. In the end, a learning/development mindset enables people to consider taking on one of these roles and to grow into the job. A "fixed" mindset simply falls back on the "traits" argument, suggesting that some are suited for particular roles and others are not. Stanford's Carol Dweck has done extensive research about how those children with a developmental mindset are more successful in school than those with a fixed mindset. I would argue that the same goes for executives. Those who simply take their talents and skills as fixed are not as likely to succeed. Those who believe that they can continue to grow and develop, even at a later stage in their careers, are more likely to thrive in various roles.