My experience with icing is that it does not stack on so quickly that you can't tell someone about it, even in severe ice you have time to ask for a change of level, descent etc. The flight profile does not really fit sudden icing, and a stall. What I do see in those two failed chute deployments is that once the chute detaches the aircraft does nose dive very rapidly at high descent rate and speed. This event seems to start from climb speed, not particularly slow, there is still some altitude gain indicated after speed washes off rapidly, and then a brick like descent, but not accelerating to what you would expect for such a vertical descent profile. That's why I was thinking maybe some sort of chute malfunction, it deploys badly, the drag link pitches the nose up while forward speed reduces rapidly, then it arcs over into a semi drag arrested descent. In any case it's a tragedy and I hope those with the expertise and more information can put together something we all can learn from. The whole thing happened very quickly, so I don't put much weight on no 'mayday' being a significant marker.