My 0.02:
The pilots must have thought they were in an overspeed situation. Horns blaring, rate of descent 10000+ fpm, no reliable speed indication, dark night, in severe weather, stall warning suddenly went off after pitching the nose up for sometime and then coming back on after pitching the nose down...
It's a pity they got it wrong. When in confused state, one would try everything to save the situation. They must have thought stick aft at full thrust was working since the stall warning actually stopped blaring. The thing they couldn't resolve was why were they still descending at a rapid rate? That's when one of them pushed the stick forward, which unfortunately re-trigger the stall warning. So they pulled the stick back to silence the horn, and the action did silence it. And all the while, they didn't have a valid 'speedometer'...