How does a L410 perform in single-engine conditions? How often NOAR pilots do sim training? Some part135 operators in Brazil don't even send their pilots to the sim.
Anyway, watching the video it seems they could be flying below Vmca and entered into a spin. Not much left of the airplane, except for the tail and left wing...left tip tank is intact, maybe an indication that there was no fuel in it and weight and balance was not an issue (or at least they were below MTOW).
Brgds