Let me use a motor racing analogy. If both cars are relatively equal it is very difficult to make up time / distance on the other car. But, if one is a high end sports car (you fill in the make/model) and the other is a Smart car, making up is fairly easy. Schleck and Contador are the former example.
The last stage is essentially a procession with a couple of sprint points and the stage winner at stake. The overall GC (general classification) goes un-contested. That being said, one of the Tour's back in the 80's, the last stage was a time trial. Everything was still up for grabs. Greg LeMond was about 20 seconds behind Laurent Fignon. LeMond, using aero technology that is now standard issue, made up the 20 seconds plus 8 or 9 additional seconds to win.
In the final stage like yesterday, teams would never challenge the leader like that. Sport etiquette.
Does that help answer your question?