Each of the 2 Stall Warning Computers receive data from both angle of attack sensors. They also continually crosscheck each other. An erroneous input from one vane triggers an event message on the display along with an audible alarm.
The Capt should have disconnected the autopilot (if engaged) in the early stages of flight problems. Each yoke has a A/P disconnect switch plus excessive manual force on the yoke disconnects the autopilot. Being that airspeed, aircraft attitude and engine power were NOT in a stall envelope, the Stabilizer Trim Setting should have been noted as way out of the normal setting for stable flight. A manual trim readjust would have saved their lives.
This is pure ‘Pilot Error’.
The manual trim adjust only lasts for 10 seconds, and then the MCAS lowers the nose again.