1: Panic. His brain's "we're falling out of the sky" alarm was louder than the plane's stall alarm. (The correct reaction to the first is the opposite of the correct reaction to the second.)
2: Mental error caused by UI confusion. "Stall speed" is shown on the airspeed indicator, and he knew his airspeed sensors had failed. Therefore, he concluded that the stall warning was wrong. (But, stall is not detected by the pitot system, it's detected by angle-of-attack sensors which were working just fine.)
3: Training. Pilots are casually taught "you can't stall this plane" because under "normal law", that's true. No matter what input you apply, the computer will not let you stall the airplane. Unfortunately, the plane was not in "normal law" at the time, because of the failed systems. (This is indicated somewhere, the information that the plane's not in normal law is available to the pilots.) I'm guessing that no instructor ever mentions those exact words in bullet-point form, but I'm guessing that someone has said, "just pull back as hard as you can, you can't stall this thing" when practicing, say, engine-out-on-departure procedures. And statements like that stick.
1: Panic. His brain's "we're falling out of the sky" alarm was louder than the plane's stall alarm. (The correct reaction to the first is the opposite of the correct reaction to the second.)
2: Mental error caused by UI confusion. "Stall speed" is shown on the airspeed indicator, and he knew his airspeed sensors had failed. Therefore, he concluded that the stall warning was wrong. (But, stall is not detected by the pitot system, it's detected by angle-of-attack sensors which were working just fine.)
3: Training. Pilots are casually taught "you can't stall this plane" because under "normal law", that's true. No matter what input you apply, the computer will not let you stall the airplane. Unfortunately, the plane was not in "normal law" at the time, because of the failed systems. (This is indicated somewhere, the information that the plane's not in normal law is available to the pilots.) I'm guessing that no instructor ever mentions those exact words in bullet-point form, but I'm guessing that someone has said, "just pull back as hard as you can, you can't stall this thing" when practicing, say, engine-out-on-departure procedures. And statements like that stick.