They were a bowl team in 2006. One that blocked a FG to beat NDSU 10-9.
Do you really think they were a bowl caliber team in 2007? Freshman QB, Pinnix hurt, starting secondary of Barber, Thomas, Collado and Jamal Harris? Decker, Kuznia, and Spry at WR. Howell returning kicks/punts. That team was so laden with talent that Brewster "needed" Theret, Thomas, Spry and Howell to fill the voids in the starting lineup.
He inherited a team that went to a bowl the previous year, not a bowl caliber team.
Also, Mason's 'good' teams largely won on the strength of their offensive scheme. Though you could argue Brew has botched it with his offensive/coordinator changes, you can't fault him for trying to implement a new offense that can better utilize the higher level of talent he was planning on bringing in.