Jason Garrett was called in by Jerry to be the new captain of the ship, no one outside the offense was familar with him. We all saw a two headed coach with one having more authority than the other (WP) but two seperate territories offense and defense. Dallas has shown to be a team that does not fare well when confronted with adversity (Romo's injury, a missed FG, etc). The team started to fully take on the personality of WP and did not seem to have a contigency plan when things go wrong.
Jason takes over and immediately starts to make changes on how the team operates in the days before the game with the giants. Jason kept the same messages: moving foward, the giants are the next opponent, and none of the teams care about the coaching change. Garrett changed the meeting times, the pratice schedule, the dress code, instituted pads practice on wednesday. An almost night and day difference on how the schedule was before, an emphasis on a quicker tempo and attention to detail.
Think about the idea of increasing tempo while at the same time they are asked to show a better attention to detail. Look at it from your own job perspective, if you new boss said I need more produciton in less time. Due to the economic situation we currently face it is probably a situation we have already seen as american workers. The time you have becomes tighter and you tend to stay later at work, but the lack of water cooler talk causes you to refocus in the ideal situation. The focus eliminates other distractions and keeps the purpose to one sigular goal, the other issues tend to fall in the background. The only thing that mattered was the next game and they had to be ready because the giants are a good team and they do not care about the coaching change.
The mentality of the team showed that they do not do well with outside distractions and refocusing their mind was more of a psychological move than the idea that making players dress up in suits would help them remember to play competetive football at a high level. It reminds me of the movie "Tin Cup", specifically the scene when Kevin Costner's character is at the US Open and is hitting warm-up shots and is still suffering from the "shanks". The caddy played by Cheech Marin sees this and has to do something drastic, check out the clip.
That scene is what I think Jason was doing to the team, taking them out of their usual element and getting them to focus on football only.