BYU hasn't done much to help the WCC yet. To have a legitimate conference, you typically need multiple teams that do well. The WCC is Gonzaga and then one more team (BYU or St. Marys) that MAY win one game in the tourney on occasion. All the legitimate conferences have multiple teams that do well in the tourney.
Obviously it doesn't hurt the WCC if Gonzaga wins, but it doesn't legitimize the conference, just Gonzaga.