>>1297546AF447 happened because of many, many different stupid reasons.
First of all, they chose to fly into a lightning storm in the route planning. A British Airways flight to London went north of the storm on its way to London and a Lufthansa went south of the storm on its way to Munich.
https://youtu.be/kja7oj5UXZgPilots are told to avoid storms. Storms can introduce windsheer, icing and microbusts.
Second of all, upon having the IAS Disagree idication on the PFD's Flight Mode Annunciator, the flight crew must have immediately proceeded with Airspeed Unreliable Memory Items and then referring to the QRH for the appropriate thrust setting and attitude angle for the altitude.
https://youtu.be/xiB1eejdgdQ?t=490https://youtu.be/GhoTVJmOmMwThird, when the Captain returned back to the Cockpit and took his seat, he started making his own inputs. This resulted in some Dual Input aural warnings, however further Dual Input aural warnings were suppressed by the "Stall Stall" aural warnings.
However, the Airbus aircraft, from the A320 to the A340 all feature a set of lights in front of each pilot which shows when Dual Input occurs.
https://youtu.be/t_R45td63qgFinally, there is one simple thing the Captain failed to do, and this would have saved AF447. The Captain failed to carry out Positive Transfer of Control. He did not say "My Plane" or "I have Controls" or anything like that. Whenever Pilot Flying ever changes, it is part of airline SOP to carry out Positive Transfer.
The single thing that student pilots are taught in freaking flight school, and the crew of AF447 forgot about it.
AF447 was 3 pilots who ignored and forgot all the memory items and SOPs and couldn't even remember the basics of flying an aircraft of any type. Don't blame it on the Airbus, it was the crew who crashed the plane, not Airbus.
