...the OP is about Bronco, not a comparison between Bronco and Lavell.
Also, not knowing who the next candidate is is why you interview, to find out who the next coach would be. Did you know before hand that Bronco would be a good coach? Nobody did. Not even the BYU Athletic Dept or Administrators. They passed on Bronco after his first interview because he didn't do well. They didn't think he'd be a good HC candidate. They had to give him a 2nd chance to interview after a bunch of his defensive players flooded the AD's office asking that he be given a 2nd chance. That illustrates that BYU had no idea if he'd be good or not but they took a chance.
That's how it works.