From the pictures....
Translating sleeves are still aft. Forward idle has therefore not been selected.
No flaps, slats or spoilers.... So no hydraulics you say ? So how did they apparently select reverse on both engines without hydraulics ?
On landing you normally select reverse idle by 60 kts and forward idle at taxy speed. Looks like these guys never reached taxy speed on the rollout. After landing cx with selection of flaps/slats up would follow selection of forward idle..... not precede it.
An inadvertent selection of flaps up on landing roll maybe ? That would stow the spoilers and make stopping far more difficult. But what would you be possibly doing during the landing roll to mistakenly select the flaps up? When landing on a short wet runway all eyes are on the decel and the remaining distance... not pulling levers.
This was a very slow speed upwind excursion where 10-15 feet of level wet grass would have stopped the jet. Unfortunately that was not the lie of the land.
Maybe the speed was under control on landing, the after landing checks were in progress and as they approached the runway end.... someone inadvertently selected TOGA? Stranger things have happened! Or simply a case of speed misjudged ?