Point being, it wasn't a high energy impact and the aircraft didn't incinerate itself after the impact with the ground. The mini liquor bottles in the serving carts survived unscathed. You don't typically see wreckage in this "good" of condition.
If not blunt force trauma, whether first/second/third impact, then likely drowning, for the fatalities. Either unconscious in their seats; or if they managed to survive, potentially couldn’t egress the wreckage? The Blackhawk was mostly intact and upside down in the shallow water, likely same fatality mechanisms.