The only way Callahan would have stayed in Dallas is if he was paid HC money. Dallas wouldn't let him interview for positions at the end of 2013 and they stripped him of play calling at the end of 2013 season. He was professional and did his job last year but no was he re-signing here.
Garrett kept interfering with his duties as play-caller and people this off-season downplayed his role here because of their agenda.
Callahan built our line and now the Reskins are running well against stout fronts like the Dolphins and Rams, with a no threat QB like Cousins in the back-field. And Fisher is coming out and saying that it was like playing the Cowboys OL again.
That being said he was supposedly going to stay, but Gruden came calling and Callahan has those ties to the family. Callahan is an OL coach there too and he has now said he prefers to stay as an OL coach.
Whatever it was, Jerry pays others big money and their is no salary cap and position coaches for such an important aspect is no joke. The Patriots have had the same OL coach got like 20 plus years and it's the most dominant aspect of their team in reality. Brady very rarely gets pressures, particularly from the interior.