These kinds of crashes are pretty rare in MT; most folks know how to drive in the winter. Usually these happen during a blinding blizzard and the vehicles slowly pile up.
The MT DOT doesn’t use much sand, they mostly rely on liquid calcium chloride de-icer. That stuff works better at lower temps than salt does. It does have one quirk, though. The CC is a thick, slimy liquid and, if it’s applied over existing ice, there is a brief interval where the slick de-icer on top of the ice creates an almost frictionless surface. That could be what happened in the case of this particular accident.