Why do they insist on searching outside the company for a "rockstar"? Wouldn't someone within the company with tons of proprietary knowledge of the organization make more sense?
In Uber's case public perception was that their structure was dysfunctional so an outsider was needed to try to make a break from that troubled past. An insider would have perceived baggage from all the scandals. Also they might need specific skills needed (e.g. IPO, growth, merger).