More top-notch awareness and tactics by Team Sky.
Because they treated it like it was a bike race?
Seems to me more like ineptitude on Aru's part than genius on Sky's.
I’m not claiming genius but good planning, high awareness on the road, and tactics and team strength to make the most of any opportunity. Astana sadly lacks all of these except reliably good tactics when situational awareness is high.
For example, did you see Sky had people handing out musettes at 20-something km to go? They were the only team doing that. All the others relied on riders going back to the team cars. In this kind of finish, where positioning is everything, that gives the Sky riders an advantage.
Read this, especially Froome’s praise of Kwiatkowski, Rowe talking about studying the video from two years ago, and Portal explaining how Kiryienka reported Aru’s position as he fell back following his long pull.
Sure, it’s all just treating it as a bike race, but why don’t the others do that then? The answer is that it’s hard, requiring consistently high effort and motivation from all team members.
Eventually that pays off as it did yesterday.