The main way to build a winning culture and product on the field is to build through the draft and fill in leftover holes through free agency and even trades. The same goes for college football, as with the integration of NIL and the transfer portal, both leagues now have similar business-like paths to success.
Prior to said implementation at the college level, the days of yesteryear required college staffs to build up their programs, almost entirely, through high school recruiting. Similar to that era, but nowadays at the professional level, GM Chris Ballard and his scouting department live and die by the draft.