Well, "personal elements" are relevant if they can help explain what happened.
Lots of very experienced pilots have embarked on obviously illegal or "impossible in the wx" flights, on what turned out to be their final flight.
I now think the plane was indeed on autopilot because the vertical profile is too good for hand flying. I could not hand fly such a constant VS, commencing immediately when the descent starts, if you paid me for it.
Which then leads to the obvious question: why did he plummet?
- autopilot failure (I've had more than a dozen and some
can be hard to spot)
- some avionics failure
- finger trouble, causing the autopilot to drop out
- turbulence, causing the autopilot to drop out
- structural failure (somebody worked out his GS at ~ 200kt)
No pilot transmissions appear in the report (which does not mean he did not make any and merely means nothing could be transcribed into text) so whatever happened kept him busy.