Jerry Jones took one drunk night to fire a back to back winning Super Bowl Head Coach in Jimmy Johnson.
He will take until Jason Garrett's contract actually expires (1-14-2020) to part from a coach that lost 4 games that decided the NFC East and playoffs in 4 different season 3 of which was in a row, was interim HC coach that finished 6-10, went 4-12, 9-7, and 8-8 the non-playoff seasons. So Garrett 10 years had 7 non playoff seasons.
Jerry Jones does not take long to make decisions. He fired Tom Landry the day he became the owner of the Dallas Cowboys and was seen at a Dallas Restaurant the night before with his new Head Coach, he meet with Bill Parcells to be the HC of the Cowboys while Dave Campo was still HC, he passed on Randy Moss even though he had a scout with plane tickets in wait for the future HOF and 100 yr All time WR, he quickly he traded a 1st and 3rd round pick for a WR that team went 0-16 and then hired the 0-16 HC as DC. So why so long for Jason Garrett.
Jimmy Johnson and Bill Parcells drove Jerry Jones crazy because to get both meant giving up total control. He eventually will get it back. But giving it up is hard. Taking it back is hard. That is the reason for the wait and stress. Jimmy Johnson hung on to full control from 1989-1994, Parcells 2002-2007. Jerry does not want to give 5 years of his late 70's to that type of Super Bowl winning Head Coach. His 12 year experiment with Jason Garrett learning on the Job to be his Tom Landry failed.
With his age at 77, the next HC would likely survive him or at least have more input with Stephen Jones and Will McClay than his input at Owner, GM, and Head Coach of the Dallas Cowboys. Cowboy fans want a GM and Head Coach not named Jerry Jones and it is killing him to lose his control he lost from his own football failures. This will take time. Jerry Jones has time (Garrett expiring contact date), and money (5 Billion dollar franchise).
You are using logic to reason with. Jerry does not follow logical thinking, esp when it comes to winning at all cost.
Jerry's top priority is to be a rock star, constantly doing interviews, constantly speaking like he's the hc (jerry IS our phantom hc btw), constantly remaining in the spotlight. Jerry, not Zeke or Dak is the face of this franchise. To relinquish control to a hc or gm is not an option on the table (i.e., even after 25 straight seasons w/o a deep playoff run) and it will never happen. To give up control is to give up his rock star status and take a back seat. His billions bought him a platform to launch his pseudo rock star act and post Jimmy he has played that role to the hilt.
You see, Jerry playing rock star, playing gm, playing hc, and micromanaging every facet of this org is his top priority, winning be damned. Well, a quarter of a century of playoff futility is not enough incentive for our Johnny Walker Blue soaked owner to try something different. If you think he will relinquish his rock star platform then you havent been watching as close as hardcore fans. Jerry may hire a strong hc who like Parcells can hire his own staff, but you can take it to the bank that the next hc will NOT have in his contract that they have final say in football matters. Only Jimmy had that in his contract, but then again he knew Jerry before getting hired and now we know why he insisted on having it explicitly written in his contract.
I'm afraid that Jerry has a "Til death do us part" pact with the fans, signed in blood with hubris as its foundation. We will never get a top notch coaching staff, will never get a hc with control. We will see the illusion of control relinquished, but the past quarter of a century says it's fool's gold. Now who wants to buy season tickets, jersey, and Cowboy's swag?