...when BYU gave him the job. Bronco was a first time HC when BYU gave him the job. Gary Crowton was an experienced HC when BYU gave him the job. Some you win and some you lose.
Lavell's success with assistant coaches was with young guys trying to make a name for themselves. He didn't out compete a coach like Barry Switzer, Bo Schembechler, Woody Hayes, Joe Pa, etc to get high profile assistants. He struck gold with up and comers who brought their drive and innovation to BYU to learn from the innovators who were already there and then left when the next opportunity for them presented itself. Eventually guys get comfortable and don't want the vagabond lifestyle and they hang around as long as they can. I don't always know that its a good thing to have your entire staff or the majority of it made up of professional couch potatoes who bring nothing new to the program and are just trying to draw a paycheck.
It's almost like having salesman on your staff who are just happy with the salary they get.