I always thought Caldwell was the type who would get the baseline out of his players. Seldom more, never less. Is that good enough to win a championship? Well if Peyton Manning is your QB, it’ll get you awfully close. He’d probably do pretty well with the Lions current roster.
On the 2019 Lions though it wasn’t going to be good enough unless we found a hell of a lot better GM than Martin Mayhew or Bob Quinn. That was unrealistic, and Caldwell was not going to inspire us to win games where the other team wanted it more (e.g., Bengals). Or to win 11 games with a 8/9 win roster. So, he needed to go.
Campbell OTOH is the type who can take a guy like Malcolm Rodriguez or Christian Mahogany, taken in the 6th round as fringe NFL talent, and make them play to the best of their ability every single game. Make them improve into starters.
Campbell will turn a 1-16 roster into a 3-13-1 result; a 6-11 roster into 9-8; 10-7 into 12-5; and 12-5 into 15-2. With Campbell, the baseline isn’t good enough.