There was a totally different relationship between the AD and those coaches. Knight was beholden to the Tech AD for enabling him to resume his coaching career, after leaving IU as close to radioactive as a coach can get without NCAA sanctions being involved. Knight also apparently wanted to leave behind a situation in which his son could prosper as a head coach, so he wasn't about to make waves. Knight was rough with players, but smooth with his AD and administrators.
OTOH, Leach created hard feelings. He did an end run around the AD last spring to get a bump in pay and an extension. By filing for the TRO to coach in the Alamo Bowl, he defied both the AD and the administration.
What I've read in local media is that the Tech side of the story is about there being a window of opportunity for the AD to get some revenge and send Leach packing, thanks to a season in which the team lost some games it should have won and a convenient media firestorm which put the coach's treatment of players in a bad light and provided cause to terminate the contract.