Because holding an upper level position in any organization in football is all about consistent results. He failed to deliver it according to management and ownership, the guy who writes their checks. Arians approach may be the same or different with the Colts, as far as i can care I can give 2 shits of what people over at Indy think of him. What matters is that his results as the coordinator of the offense didnt satisfy the fans, management or ownership. Its as simple as that. I for one dont care about Arians anymore, hes not with us, he can do whatever he wants, I feel like hes more butt hurt than we are, so some of the people still bashing him need to move on. But at the same time the lack of the consistent running game leads to Arians lack of committing to the run game.
Just watch the 02 divisional playoff game against the Browns. Browns explosive in the beginning, running on all cylinders in the first half. Couldnt seal the deal, couldnt run the ball. gave the other team an opportunity. Lost the game. Guess who was the OC? yep