[Amended Report] On 2 January 2015, the commander of a Saab 340 suddenly lost directional control during a within-limits crosswind take off and the aircraft left the runway onto grass at approximately 80 knots. No call to reject the take off was made and no action was taken to shut down the engines until the aircraft had come to a stop in the soft ground with a collapsed nose gear and substantial damage to the propellers and lower forward fuselage. The Investigation concluded that the most likely explanation for the excursion was the absence of any rudder input as the aircraft accelerated.