Re: The investigation should center on...
" I'm don't recall a single simple hardware failure leading to a crash of an Airbus plane"
Kind of a combination of both, but a frozen up attitude vane (measures the angle of the plane relative to the airflow) led to the anti-stall system not noticing the plane had stalled and doing nothing about it.
Daft thing is they were testing the anti-stall and had deliberately stalled it. I can't remember why they couldn't recover it - possibly just ran out of altitude trying to make the anti-stall do it's thing.