Further to my previous post, a possible scenario might be (and in no way am I suggesting that this did happen):
Aircraft flies through heavy weather and encounters turbulence and icing.
Pitot probes ice up resulting in numerous system failures.
Aircraft flies into a suddenly warmer airmass.
Autopilot maintains constant Flight Level, but with increase in OAT and increased weight due to ice build up, engines are at max thrust and can't maintain airspeed.
Crew are distracted dealing with the system failures and don't notice or have no reliable indication of decreasing airspeed.
Icing on wings results in a higher than normal stall speed.
Ice build up is asymetric so one wing stalls before the other.
Spin ......
