Multiple times, I've seen inoffensive personalities be internally promoted to C level positions ahead of more politically savvy (and often more effective) candidates. This often takes place after the departing executive has a strong personality or leaves for contentious reasons. Everyone wants someone nice and trustworthy and unambitious to take over so that the organization can heal. I'm guessing this is what happened at Twitter.

How to maneuver into this position? Maybe you could get hired to an important role at an organization with an unstable CEO, and make sure that you are friends with everyone and don't piss anyone off. Then wait for the CEO to lose their shit completely.