One of the great parts about college football is its constant change. Players have to wait three years between graduating high school and declaring for the NFL draft, which creates enough time for stars to develop while also leaving a regular cycle of talent moving in and out of college lineups. Combined with graduation and transfers, college rosters have a significant level of turnover.
This can be good for fans, at least those who are open to new, exciting things. The movement gives new talent an opportunity to emerge on a yearly basis. Some might be expected, but some of the emergences are more surprising.