The upset here happened promptly, and the IFLOC went into a severe vertical departure pretty promptly. Those are very high rates of descent for an aircraft of that design. The GS is modest as the descent angle is very high, CAS is high. The system architecture and the availability of ADSB data suggest that electrical failure/instrument failure is unlikely the primary cause, flight crew incapacitation by hypoxia is unlikely at the relatively low altitudes that this occurred at, it hadn't spent great time above 10K, and stuff went odd at 05:11:41z and bad around the 19,000' - 19,400' reported altitude range. Flight crew incapacitation from an emergency medical event is another matter.. Spatial disorientation in turbulence may be a factor as it can always be.
An initial inflight break up would be a possibility, the RH outer wing panel would be a target for close scrutiny, but this aircraft would most likely have failed in flight later, close to the final impact point, it would be surprising if all pieces came to rest at the one location anyway. Pilatus make a strong aircraft, but rotors and waves can make for bad days out.
Sad end to an intended lifesaving exercise.
Juan's analysis on Blancoliro raises some interesting points, that is the right hand turn at 05:11:41z has hallmarks of a spatial disorientation event. SPIFR, in turbulence and accelerated flight, particularly with rain/snow impacts on a windscreen, and with light reflection off cloud layers, getting disorientated is quite possible. It's unpleasant enough multi crew, but single pilot, it's nice to have a good APLT and a really nice set of ADIs and standby's.