Why is everyone fixated on a stall/spin?
If the pilots lost attitude reference or couldn't reconcile which one to use, the default maneuver in instrument conditions is a spiral dive even if the loss of control began with a stall. A spiral dive will get the airplane from 35,000 feet to the water in less than a minute. The airplane won't come apart even if it goes supersonic if the computer is restricting load factor. If that's in fact what they got into, they could still hit wings level and flat at a high rate of sink if they finally got attitude reference back but too late to completely pull out.