3holelover,
IMO Airbus SAS failed: There are some ways to present to the crew an imediate understanding and even ways to keep a/c in Normal Law after UAS (an old and well understood problem due sub heated pitot's). The plane certainly worked as designed wrt to AS. The design could be improved, was not (wrt to UAS) and eventually Murphy Law put all elements together at that night.
IMO the first slice ("swiss cheese") was this Airbus SAS failure. A latent failure. Their a/c are designed to operate for random (time) failure of Pitot tubes and NOT simultaneous (brief) erratic data coming from the redundant sensors. This certainly was consider highly improbable in the design. But the 30+ UAS cases before AF447 should have alerted to a rethinking of the design from the designer/manufacturer. A simple one as we could imagine.
And the patent filing (of an AS laser device, posted earlier) from Airbus SAS was made months AFTER F-GZCP loss.
The importance of AS is considered so high, there are THREE redundant elements supplying this info to the a/c.
IMO just to rely on Pitot's replacement (to another model also prone to "fail"), and operators crew training was insufficient for the company that introduced FBW (and a/c new control philosophy) in commercial aviation.