Bear
IMHO they were convinced of overspeed. Nose up, give me all the stick back you got, why does she stop at pitch +16 deg, I want more. Deploy spoilers. Idle the engines. Crazy speed.
What made all three believe in overspeed. To the extent that they can ignore stall warnings, the UAS procedure, ignore the high pitch, low IAS, low ground speed, ambient noise changes. Was it the deceleration giving them the perception they were in a dive and PF thought the attitude indicators were wrongly showing +16.
Something made them all convinced of it. Did the PFD show the red black overspeed ladder?
Even a sceptic has to wonder if there was something else they saw that we do not.
I might believe one or maybe 2 had it totally and insanely wrong but not all 3 pilots.