Gross oversimplification. BB was a good enough manager to employ and listen to Rehbein, who scouted Brady. Brady was not very good at first, but BB could see his potential and kept 4 QBs that first year--almost unheard of, but it was because he recognized something about Brady he really loved. In year 2 BB knew Brady was better than Bledsoe, but Bledsoe had just signed a 10 year mega-contract so he couldn't start Brady, and they needed to fill seats in a new stadium. BB had the sack to stick with Brady when Bledsoe came back from that injury, even though he was cleared to play.