Carr is a franchise quarterback and was drafted as such. And last season he delivered. Frankly the Raiders have improved under him every year. Kaepernick was not drafted as a franchise and inherited his job because of a concussion. He played very well, but it isn't as though his performance was so much better than Alex Smith and certainly hasn't been since he went to the Chiefs.
The Raiders were 12-4 last season. Carr was injured at the end of the season and without that injury they were probably the second best team in the AFC and would have been a great match up for the Patriots (if they found a way past the Chiefs).
The Raiders are making a commitment to building around him and it shows.