There is another very hypothetical possible cause factor which fits the little pictorial and other public media and preliminary report evidence available.
Background: the AW139 rotorhead incorporates leading edge pitch control horns i.e., the push rods are attached on the blade leading edge side. Same as the CH-53E.
The 1996 CH-53E fatal accident on the first hover of a standard production machine was traced to a bearing failure ( caused by a manufacturing defect in the supplied bearing ) in the rotating swashplate. One can easily imagine the rotating swashplate slowing down and the effect on rotor control. Those words imply it happened gradually, but the final bearing failure happened quickly and part of the result was that the blades chopped the tail off, while the remainder of the machine descended vertically from the 150-200 ft where they had been hovering. I had been walking toward the rear of the pilot office ( which has a somewhat cut-off view of the field ) and heard three distinct thumps, turned around and caught a glimpse of the machine before it disappeared behind a storage shack. The rear tail section was separated.
I’d imagine the NTSB will as a matter of course look at the swashplate bearing and ensure it still moves freely.
PS: the reason I used thee term “very hypothetical” is because the difficulties involved in design/manufacture and QA on a huge swashplate bearing as on the 53E are quite different than on much smaller vehicles.