Wings have a very delicate engineering behind them. If the airflow over the wing is disturbed too much you can lose lift and stall the wing. Plus ice build up on engines and instruments could mean bad info to the pilots and not enough power to get out of it. This was a prop driven plane so those are airfoils too. Ice on a prop and you might have no thrust to keep going.

It’s a flat spin. It’s unrecoverable for many 2 engine aircraft. Sounds like heaving icing was reported between 12-21000’ this morning. They had been in flight for over an hour. Scary stuff.