Darabont had right to be upset because AMC was making like 8 million in profit per ep that first season and were still trying to cut Darabont's budget.
I remember one of the final straws before he was fired was his refusal to cut out walkers. Some exec suggested that no walkers be showed only heard so they could save on makeup cost or something like that and he constantly had to fight for money against Mad Men. Darabont was responsible for the cast of great actors and after he left seasons 2 and 3 suffered for it.
The Prison/ Governor arc would have been so much better with Darabont because he's more of a walker action show runner than the current guy (Scott Gimple) who likes his character development to be the star although season 5 has been a great balance of both.