Just to add to the speculative frenzy:
-- If one thrust reverser were inop, it's easy to see how things could go wrong in a hurry. We're all creatures of habit, and many accidents that are attributed to pilot error involve either the inappropriate application of previously learned habits or some break/interruption in a previously established habit pattern that results in inappropriate decisions/actions.
After touchdown and normal landing, the pilot would have both engines near idle, then select thrust reversers on both and increase power on both (to reduce speed thereby decrease wing lift and get more weight on the wheels thereby increasing the effectiveness of the brakes.) With one inop reverser, if he went through the same motions the plane would yaw a lot and it would not slow down--it would speed up and the wheel brakes would be largely ineffective, especially on the wet runway. The first thing he'd likely suspect is a problem with the antiskid system, which is not at all what the problem was. But, with flaps at full, possibly spoilers deployed and only getting partial thrust for an undetermined reason, figuring everything out, getting the airplane properly configured, and getting off the ground in the remaining runway would be dicey (particularly given the tall buildings nearby).
But, in a few months we'll know exactly what happened. I would be surprised if the final findings don't pin a large amount of the blame on an insufficient appraisal and briefing prior to final approach concerning what-ifs given the situation at the airfield and with their airplane.
Very sad for all concerned.
Aviation is really simple--until it isn't.
