It is entirely possible that a dominant dynastic basketball program in fact has NO assistants who would be above average P5 head coaches in their own right. That is not an impossibility at all.
Not at all, big name programs actually groom assistant coaches with their culture and experiences of success, but it is also the fact that some of their coaches "push" their own candidates and are some of the most influential figures in the coaching profession. Coach K is arguably (and IMO) the most influential person in college basketball, definitely in coaching, way beyond Duke's on-court success or the pure value of an assistant.
There is also some commonality and culture in hiring decisions. UI has never been a risk-taker, high risk/high-reward decision maker. Everyone wants the A+ candidates, the hot names, e.g. Shaka, Stevens, Bennett, etc. The culture is defined, however, by the decisions schools make when that pool dries up. Look at Marquette, for example. It is no coincidence that some of the risk hirings we have talked in this thread, Wojo, Buzz, Crean, etc. all come from the same school. VCU has a similar culture, at mid-major.