Originally Posted by
quentinc
I would imagine the forces at the stabilizer, played some part in the setting of VMO, which had now been exceeded.
The aircraft was more-or-less level and only just above Vmo at the point where those two brief applications of trim occurred.
The widely quoted 500 kts was subsequent to that, the result of the last episode of MCAS AND trim kicking in and the unrecoverable descent.