That's because he is a retread. But that doesn't mean he can't be successful. I'd be more concerned if he had failed in his prior two jobs, but he didn't. He got pushed out in GB by Rodgers and he essentially left Dallas because of Jerry. And he had a 12-5 record 3 of the last 4 years. Even last year he had 7 wins when they had a ton of injuries.
This isn't like hiring DA who had a really bad losing record with the Raiders.