A few posters here seem perplexed at how a pilot wouldn't "instinctively", or "reflexively" reverse his pitch trim inputs after the aircraft rapidly entered the dive.
These posters perhaps don't understand human behaviour very well. Put a human under enough stress, and they won't make the same responses they would have when calm.
Here is an example. In 2004, a pilot of an Aerocommander AC500S engaged the autopilot shortly after reaching top of climb. Unfortunately, the design of the human/machine interface in the case of this autopilot was very poor.
The autopilot immediately pitched nose down, and proceeded to wind on full (or near full) nose-down trim. The aircraft, in a steep dive, exceeded limit airspeeds and disintegrated in flight.
ATSB investigation report here:
https://www.atsb.gov.au/media/24274/...400610_001.pdf
It appears that the pilot was startled by the immediate and violent pitch down, and responded by pulling on the CC - rather than by disengaging the autopilot.