He was a consistent winner at BYU
He has one of the best defensive minds in the entire country. He generally made teams beat us with schemes they didn't like to use.
He was adaptable. He used to never go for it on 4th down, but then changed later in his career.
His players loved him and would run through a wall for him. I have spoken to many and he was beloved among those he coached.
Did Bronco have his flaws? Of course. But that isn't the question you asked.