You know, cyclingnews has live coverage of their own on every stage. It's great because it provides a complete record of everything that is happening. Let's take a look shall we.
So, Contador crashes...
You are correct, Astana started setting the pace.
But the gap falls from 4 minutes to 3:30
And he keeps having to go back to the car for medial and mechanical support.
Astana on the front by this point.
And yet, with Astana on the front and Contador keeping going back to the car, gap is still falling.
Peloton riding tempo, not going ballistic.
Getting closer to his DNF now, surly he's starting to really hurt. And starts losing time. Astana had to at this point move to maintaining the gap to Kwiat.
And he's out. Slowed down in that last 10 minutes before his DNF. But it took over 10 minutes for the gap to start going out again from when he first crashes.