He was 19 miles out on approach, looking at the temperature and spread on the ground at the destination it's pretty safe to assume he was picking up a load of ice at altitude in light rain and clouds, was probably flying on autopilot and didn't notice the incremental changes in trim and handling, and by the time the AP couldn't manage it anymore and disengaged he was in command of an essentially unflyable machine. He also had four passengers and probably luggage, so W&B may have been a factor re spin recovery... plus the fact that nobody has been trained in actual spin recovery for the last few decades. Even back in the 80's I had to strap on a chute and take an aerobatics course in order to get mine.