When max thrust is applied at low level in an airliner at landing weight, the human vestibular balance system will perceive that longitudinal acceleration as a pitch-up, especially in the absence of strong visual cues (ie, good VMC flight conditions).
The instinctive pilot reaction to longitudinal acceleration is to push the control column forward to maintain what he perceives as a necessary control correction to maintain a constant aircraft pitch attitude. This reaction is especially strong if the pilot has been flying with visual references and then subtly loses such visual reference and enters instrument flight conditions but still believes that he is in visual flight.
The secondary effect of thrust application is also an upwards pitching moment on the aircraft and this reinforces the need for the pilot to instinctively push the control column forward (and trim) with any thrust increase.
This principal of fooling the human vestibular balance system is employed in 6 axis Flight Simulators to imitate the motions of aircraft flight.
Perception of an increasing pitch up by the pilot flying in response to the increase in thrust may have triggered him to push the control column forward until such time as he recognized the actual very steep pitch attitude on re-attaining strong visual cues on exiting the cloud base in the subsequent dive.
This principle might be a factor in the subject accident.