To answer your second question. AC had no obligation to Lance personally, but he does have an obligation to his team and attacking on the first mountain stage isn't necessary. All the GC contenders were sitting together. Why do that? It doesn't make sense to me. Especially since none of the GC contenders at the time were near AC in the overall. Cancellara had the MJ (not an overall contender), Lance in second, AC in third, Kloden in fourth, and Levi in fifth. Your team has four of the top five spots, and you're going to attack to gain 21 seconds when your behind a teammate by 19 seconds? Makes no sense. He had 6 mountain stages and another ITT to make up time.
One it was in Spain and he's Spanish. Two, with the team leadership hanging in the balance and Armstrong & Bruyneel already clearly showing who the team strategy is geared to optimize who's chances of Tour success (Armstrong), sometimes its necessary to improvise on the road on the "strategy" that was set forth that morning. Three, they had reached the 2 or 3 km to go point before the summit finish and the only attacks were the weak ones from Evans and Van Den Broeck. The other contenders weren't feeling the strength to try to lessen their time disadvantage by attacking, a sign of weakness to an aggressive rider like Contador who was chomping at the bit with pent up energy. His attack gained him additional
seconds to his advantage on his opponents. Four, in grand tour, any opportunity to gain time on their opponents that presents itself should not be passed up if one has the legs to do so.
I mentioned this in another thread weeks ago but there was a blatant contradiction in the Astana strategy that surfaced the day of the TTT and then right after the stage to Arcalis. Bruyneel stated how great it would be for Armstrong to be in yellow after the TTT if Astana were able to gain enough time to snatch from Cancellara. Of course they were unsuccessful by the shortest of margins. There was no mention of the potential for early fatigue as a result of defending the yellow jersey until after Contador's attack on Arcalis.
It was actually their plan to try to reel in the break that included the eventual successor to Cancellara in the yellow jersey, Nocentini. It was still their hope to get Armstrong in yellow until they saw that it wasn't likely that they would be able to catch the escapees. It was only after Contador did what everyone watching, participating, working the event, and even the announcers knew that he was going to do and attacked on Arcalis that the Bryuneel/Armstrong contingent began crying foul about what disservice may have done to his teammates had he made it to the summit seconds earlier. Oh what a disservice!! His teammates would have had to defend the yellow jersey just as they would have had to do had Armstrong/Astana crossed the line a second earlier in TTT. Its actually an insult to the basic intelligence of all that were paying attention to the drama that ensued, with the exception of those that are so blinded by all that is pro-Armstrong and refuse to see the facts that are plainly in front of them.
For me it was simply a rider that saw the writing on the wall and did what was necessary to regain what was rightly his. Armstrong and Bryuneel said that it would all be decided on the road but when it was finally decided they wanted to cry foul. They tried to break & contain Contador in an effort to maximize Armstrong's chances for success which is contrary to everything I've ever learned in my +2 decades of following this sport. They were trying to create a pretty picture of the great champion making a triumphant return to the sport. They had the script prepared but Contador didn't like his part, started improvising on his lines and stole the show.