I imagine the footage of one or several cameras on on board will have been reviewed by now as well. No doubt light has been shed on cause. Speculation perhaps they will have revealed one of a couple of scenarios.
Premature deployment of a parachute causing loss of control followed by structural failure of both tail and wing.
Loss of control after inadvertent or otherwise entry into IMC with a subsequent overstress on attempted recovery. It's so easy to find yourself in a spiral dive after being distracted by the jumpers. Don't ask me how I know.
Ice could be a factor too if in cloud. Even in the Summer months.
A stall, spin on the run in is possible but most likely a few people would have got out in that case. Besides the Airvan has a docile stall even with everyone crowding the exit.
As I said speculation but borne of experience flying the Airvan on Skydive ops.