I think we can go back to the "holes in the cheese lining up" accident model proposed by Prof. Jim Reason ..... The BEA report identifies 4 big holes in this particular cheese (and a few smaller ones....): none of them big, jagged, sudden holes, but big enough to let a nasty smell though if they had lined up - 3 ATC holes, and 1 Pilot hole. Which, by multiple decent situational awarenesses, enough decisive participants, a big sky, and a happy dose of luck, they didn't. Long may that last.