I don't think the O2 ejected the passengers, reasonably theory that it is, and they may not have had O2 onboard not being a "P". I reckon it was just the force of the impact which destroyed the aeroplane and threw the seats out.
I *expect* the pilot had a fair few hours, certainly enough to get insurance on a Baron, which would mean he was reasonably experienced.
I don't think weather was a factor in this.
Fuel - surprisingly there doesn't seem to be much evidence of spilled fuel and you'd expect that with full tanks and those hot exhausts laying around that there would have been some fire with full tanks. All the fuel tanks must have ruptured duing that impact spraying avgas everywhere. It might have been luck or the pics may not show properly.
Barcli brought up the point of the Baron wing spar AD - that could be a likely cause if the wings folded up.
Pressing the rudder pedal? Hmm, it has happened before but it is a long shot. Besides you wouldn't enter a flat spin if flying at Baron crusie speed and deflecting the rudder pedal and would probably break something on the back of the aeroplane.
Maybe....he just flew into the ridge while trying to get some nice close video or pictures....?
It is a mystery.