Since the plane is greatly damaged or written off due to the crash investigating the cause is going to be tough. It may have been something you did that was missed by the club "inspectors" or it may have been a set of joints in the wing that were not glued well at the factory or it may well be that Doc316 hit the nail on the head and you just flew it too fast for the type of airplane. If a control horn busted away or one of the pushrod ends of the servo to aileron surface let go the resulting chaos could easily drive the wing into major flutter and quick destruction. The fact that it survived and did well in the previous flights and only did this during your flight where you were visiting the high speed region suggests that this is likely the case. The weakening may not even have occured right at that moment. If you were doing some higher speed dives earlier and then did a moderate but still higher speed dive or pass but did something like commanded a flick roll or whatever it could be the straw that broke the camel's back.

Sadly this newer class of 3D model does come with a very definite Vne and it would appear at first glance from your admission of playing with higher speeds that you found the limit.