I believe he was shelved while he was in prison and that was his excuse ultimately. Of course the Gambino family of that era in particular was still a dysfunctional mess still trying to recover from the Gotti era, even as John & Peter Gotti remained the titular bosses.

DiLeonardo's defection seemed to me like one of those totally preventable flips that wouldn't have happened if the family had strong leadership on the street at the time.