fwiw, i agree with most of the points in @Fomite’s response below. the people i’ve known fall into a perverse version of his “ego” point.
they felt that when they got tenure they “won” and their “ego” was strong enough to allow them to ignore the disapproval of their peers for not doing the conventionally expected things. they felt that they knew better in their hearts what the discipline truly needed and that the rat-race of establishment approval wasn’t it. so they turned inward. which is not necessarily the healthiest path imo.
they felt that when they got tenure they “won” and their “ego” was strong enough to allow them to ignore the disapproval of their peers for not doing the conventionally expected things. they felt that they knew better in their hearts what the discipline truly needed and that the rat-race of establishment approval wasn’t it. so they turned inward. which is not necessarily the healthiest path imo.