Pilots need to be designed back into the loop.. with the computer monitoring us.
Bring on the dog; ah, but it's there to keep us out of the loop. Tacho's in the cockpit? They've already thought of cameras; add a motion sensor and an alarm; job done.
It is highly possibly he believed the aircraft to be overspeeding given the lack of airspeed information and an audible warning that went away when he applied back pressure.
This has been hashed about already. It's a very modern a/c with ground speed read outs. The lack of air-speed is a red herring. What was the ground speed readout? Back to basics. If you are not sure what is going on you put the a/c into a known state and wait & watch; generally level flight. Pitch & power and assess. If you don't know the basics it's impossible. There in lies the root cause. BASICS!
It's like the various crashes with blocked tubes. The instruments might work in the wrong sense. Back to Basics. Level flight at a known power setting. Gently move the stick and watch what the instruments do. If they are obviously daft then assess, but don't start pushing & pulling is gay abandon hoping to finds the exit to the maze of confusion.