They lost Orchard, Rowe, Potousi (OL), and several receivers, but the rest of the team was left intact. When you can keep your entire lines together without losing your QB, then teams get better 80+% of the time.
That said, I don't think anyone expected them to compete for the conference championship (And I'm still not expecting it as much as hoping we can beat Cal and look good this weekend), but I think most people expected them to be improved this year.