Pulling the CVR/FDR breakers and then initiate descent a few minutes later would be... suspicious I would say. It is very hard to explain a scenario along the lines of "the aircraft suffered rapid decompression and lost the flight recorders in the process" even if it would be possible to argue about damaged wiring as a cause of the recorder loss.
To me, CVR/FDR circuit breaker pull followed by a "bad event" is just too much of a coincidence for an "accident" scenario to fly.
It is the same thing with theories along the lines of "failed door" that has been posted in the thread. I would say that based on the available data, i.e. a normal climb to cruising altitude, no pressurization problems, captain leaves the flight deck, the autopilot is set to a very low altitude and descent being initiated followed by a failure to allow the captain to enter the flightdeck all points in a very specific direction.
I just don't believe in strange coincidences and "random events" such as:
1. The captain leaves the flightdeck.
2. Some "event" takes place and the F/O reacts to it by selecting the A/P to the lowest possible altitude.
3. As some kind of "bad luck", the flightdeck door jams, thus preventing the captain to enter the flightdeck after his lavatory visit.
4. The F/O becomes paralyzed by the "event" and/or becomes unconscious and never hear the attempts from the captain to re-enter the flightdeck, the repeated calls from the ATC and finally the GPWS/TAWS "Too Low, Terrain" and "Pull Up" warnings.
The only thing I could think about, if everything else (the door problem...) is disregarded is an event where the F/O becomes dizzy and then mistakenly turn the knob to "100 feet" instead of "10 000 feet". Even if we would assume something like a "fume event" making him dizzy and drowsy, the problem lies with the related door event (locking etc).
Especially the combination of an incapacitated F/O, which just re-set the A/P AND a door malfunction at the same time, exactly at the "right/wrong" moment is a very... low-probability event and therefore hard to believe. It feels to me like talking about a failure of the generators on engine number 1, loss of APU and then engine failure on engine number 2 and then insist that an accident was caused by this exact failure to the power generation onboard.
Another one would be loss of the FBW AND all hydraulics at the same time and then use it as a "number 1, main thesis" in an accident report or investigation without having concrete proof.
To me, a deliberate act would make "sense" out of the available data. Different technical failures would produce a different outcome. I have a hard time to find any failure that could explain the course of events, especially one that would be initiate the A/P setting selected. In any "incapacitation" scenario, the captain would have been able to regain access to the flightdeck and in this case we have data indicating not one but two deliberate activations of the door lock....
It had been better if the CVR data had been withheld for further analysis before being released but I am afraid that the final conclusion just can't be anything else than a deliberate act involving an autopilot re-set to lowest possible altitude followed by an open descent until the aircraft impacted the mountain paired with prevention of flightdeck access for the captain.