Jerry hired Parcells because he had no choice. He was trying to get financing for AT&T Stadium, and after firing Johnson, he'd run with puppets Switzer, Gailey and Campo. They'd been 5-11 for three straight years and nobody was willing to put money into a stadium for a team losing like that.
So, he hired Parcells and actually let him coach. Guy did pretty good, actually going to the playoffs with Quincy Fucking Carter at QB. Remember, Jones went ape shit over Carter, and swore he was going to be the Cowboys QB of the future. Best quote I heard on that was, "drafting a fourth rounder in the second round doesn't make him a second rounder."
Anyway, Parcells found Romo, and had the Cowboys playing reasonably well, but not outstanding, when Jerry closed the deal on financing for the new stadium. The day after, over Parcells objections, he brought in Owens, declaring that he'd been busy with the new stadium, but was now going to be back to being involved with the day to day running of football operations. Parcells quit at the end of the year, and since then we've had Wade Phillips, Jason Garrett and Mike McCarthy.
Jerry started cosplaying as a coach before the term "cosplay" existed. He had to fire Phillips, cause the guy was so shell shocked he went into a presser and answered every question with "I don't know, including one about who they were playing the next week." There was no reason for him to fire Garrett, cause Garrett was the perfect coach for Jones. He faded into the background, did what he was told, and ran all the day to day stuff while Jerry strolled out to cosplay as coach every so often. Remember when Jerry ran down to the sidelines and told Garrett to take Romo out of a game cause he was afraid Romo would get hurt before the playoffs?
So, fire McCarthy, and bring in whoever you want. it doesn't matter.
This is the head coach of the Dallas Cowboys...forever. and ever. and ever.