The greatest difference between teams that do well in the playoffs and teams that do not do well is team culture, specifically that part of team culture that respond to the postseason.
On the great playoff teams now and in the past, it is like the military increasing their readiness posture in the event of a possible conflict. All leaves are cancelled. The military bases are closed to non-military personnel. Information becomes more guarded. Discipline is enforced more harshly.
Players don't spend time between playoff games on some tropical beach. They are taking care of their bodies, studying film and perfecting their gameplan.
Every member of that franchise, from owner to laundry guy, is singularly focused on their next game. They are not messing with podcasts, promoting their brand, or making themselves available for extracurricular engagements or special guest appearances. They do the PR that they are required according to NFL policy, but they don't want unnecessary distraction.
I say this in the general sense. There are always those few that can't control their narcissism.
This focus has to come from the top, typically the HC or even the GM. We saw this with the Landry teams of the 70's. We saw this with the Jimmy Johnson teams in the early 90's.
The problem is this culture is the polar opposite of Jerry Jones's mentality. He has to break players concentration with ridiculous circus acts. He has to put on a show that forces the players to entertain rather than prepare.
Both Jerry and his teams have underestimated the intensity that other team exhibit in playoff games against the Cowboys. When it is the playoffs other teams demonstrate that "do-or-die", "every play is critical" attitude. The Cowboys don't even realize they are supposed to do the same.
In almost every playoff loss, the other team jumps out to a two score lead in the first half as the Cowboys appear to be in shock. It looks like a college team playing against a junior high school, very demoralizing. With the exception of some late game heroics, the playoff game is over after the first drive in the 3rd quarter.
Often, the Cowboys do worse than choke. They don't show up and are forced to catch up just for the opportunity to choke. I don't think they are nervous when the game is on the line, I think they are exhausted from having to expend additional energy to compensate for the slow start. They have nothing left in the critical final minutes of the game.