Practically impossible to say anything constructive with what is available but surely speed(low or high)must figure highly.
For what it's worth, "Le Monde" claims through a unnamed source that the plane was overspeed and that an airbus directive will be published ASAP regarding speed management in rough weather.
This must be their starting point for this investigation..As you approach rough air,you reduce to Va which puts you halfway between low speed and high speed buffet on the speedtape.The higher you are the closer these two will be(hence the reason for flying 2k below opt alt when turbulence is expected).So less margin to counter any speed excursion caused by turbulent air penetration.If you lose electrics concurrently,then you will have to rely on standby ASI which will give IAS only,so one of the first things a pilot should mentally check approaching rough air is the IAS equivalent of Va in case he has to fly it manually.The key is accepting alt excursions and concentrating on att vs speed.CWS R and CWS P are recommended but of course you need the AP.As with so much in flying,speed is often the killer.
All comments made with reference to Boeing aircraft.I cant comment on how the scenario plays out in a scarebus.But a plane is a plane is a plane.