Depending on some variables such as a/c speed and the amount of water on the runway, without spoilers, there is a very strong chance that the a/c was aquaplaning when brakes were applied. The video evidence shows that there must have been some standing water as the spray pattern from the operating reverser is very noticeable.
If it was aquaplaning, there is very little chance that the brakes would have had any significant effect until the wings were travelling slow enough to stop producing any lift. At 94kts, I would have thought there would still be significant lift and if only the spoilers had been deployed, they may have had a fighting chance of stopping within the boundary of the airfield or at least gone over the edge with less energy.
Can the ground spoilers on the A320 be deployed manually if they didn't do so automatically due to the thrust lever positions?
Edited to add: I realise that had they retarded the #2 thrust lever, system logic would have deployed the ground spoilers and activated the autobrakes. But... as a mere Boeing pilot, I am only used to having a great big handle that can be manually pulled up at any time which will, depending on air/ground logic, deploy the spoilers.
I think that this is where some Airbus and Boeing philosophies differ in that if I were to use the speedbrake (spoilers) when I shouldn't such as when in landing flap configuration whilst still airborne, I will get a warning. From my understanding of the A320, you only get the spoilers when the system wants you to have them. It can't be overridden. Please correct me if I'm wrong.