The evidence so far may well suggest a more likely particular cause for this accident.
However, it is possible that there are other explanations. For example, suppose the engines came back to idle for no apparent reason and the aircraft went into Open Descent (a known software issue on the A300 for example, although I haven't seen it happen on the A320 yet).
Suppose the very inexperienced First Officer couldn't understand such a rare malfunction with no ECAM to guide him and this induced panic/anxiety that brought on a heart attack or stroke that left him "breathing normally" on the CVR but he could have been unable to move or speak (this is not uncommon with stroke or heart attack victims).
Meanwhile the cockpit door could have been incorrectly programmed with the emergency code and so the one the crew tried to use to enter didn't work (this has also happened). When did you last check the emergency code worked on your A320, that's if you even remember it?
Let's not forget that it's heavily in the airline's and manufacturer's interests for an accident to be blamed on incorrect or inappropriate pilot action. Yes these "holes in the cheese" are very unlikely to have lined up, but it's nevertheless possible.
It's interesting that with the commotion in the cabin, terrain warnings and then the GPWS going off and with the ground rushing towards him that he managed to breath normally whilst supposedly fully conscious despite supposedly having mental health issues.
I'm also interested in what the transponder Mode S reported to ATC - did ATC see a radar return whereby the altitude was wound down below MSA for example as the aircraft began its descent? Were ATC to be heard questioning him on the CVR as to why he was descending to such a low altitude? Or was no such lower altitude selected? Maybe he used V/S ... ?