Anytime you can hire the 65 year old passing coordinator from a team whose main weakness was its passing, you've gotta do it.
Honestly, I think this was a fall guy hire. They know this team is going nowhere fast and probably in line for a nasty, lengthy rebuild, so they hire a guy who is essentially set up to fail knowing they'll fire him in two or three years once they've been able to accumulate some talent with their picks next year plus whatever they get for trading off Watson and all their vets.
And this guy isn't some promising young coordinator who could have his career derailed by failure. It's an NFL coaching veteran who will be able to step right in to another position coaching job after he's fired. Culley has nothing to lose here. It's free money. If he succeeds, he wins. If he doesn't, he still makes a hell of a lot more money than he would have otherwise and can likely go right back to doing what he was doing before if he gets fired.