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

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).