Definitely mortality. For those unfamiliar with how org structures work in academia/tenure... (at least, assume this is still true) Once attaining tenure, you

Definitely mortality. For those unfamiliar with how org structures work in academia/tenure... (at least, assume this is still true) Once attaining tenure, your promotion track focuses on faculty leadership positions. These positions are selected by a combination of administration & faculty. It varies institute to institute, but strong candidates usually have backing from both. These positions are almost always held by tenured faculty, as non-tenure is looked down upon for historical/political reasons. Note: You only need to please 2 types of stakeholders: administration & faculty. Ergo, the path to promotion becomes: - Make tenure - Politick with faculty colleagues - Politick with administration - Wait for someone to die This leads to a weird bent where your bosses (faculty) are selected for their ability to navigate political winds and say the thing that most people agree with, moreso than being disagreeably brilliant.