I graduated in '88 and think that it transitioned in my 4 years of attendance.
The Slush Fund scandal ('67) kneecapped both programs. Football only came back briefly in the early '80s under Mike White and then '88-91 under Mackovic. Basketball, however, maintained strong teams in the late 60s before declining in the early '70s. Lou brought it back fairly quickly and sustained the success.
Regarding football, IMO you can't minimize the negative knock-on effects of Neale Stoner being forced to resign as AD in mid-'88 after hiring Mackovic the preceding winter, Guenther assuming interim AD duties, and then Mackovic, a stellar coach who gave us three strong seasons from '88-'90, becoming the full-time AD.
This meant that when Mackovic left for Texas in Dec. '91, we lost both our coach and AD. Accordingly, we lacked a stable, strong AD to hire a new football coach, and made do with Guenther promoting Tepper. Then Guenther took the AD role by default. That began the long decline of what had been, briefly, a resuscitated football program.
My recollection of the history. Feel free to correct my possibly addled memory.