Several possibilities come to mind. Being that much of the aircraft is intact and/or available and the fact that it didn't burn will be a big help to the investigators. It could have been a major electrical issue; wiping out flight information and even communication. If it was a severe enough electrical issue the pilot might have intentionally shut down all power to stop or mitigate smoke or fire; that potentially could have caused other problems... It could have been a configuration or trim issue on the go; who knows? When I had my experience with an electrical problem, quickly followed by a cockpit full of smoke; I sure did not mess around pulling CB's and such. I shut everything down by feel, ran the drill as best I could and hoped for the best, not fun... Regardless, I do think the NTSB will come up with the correct answer on this one.