Consider the factors known to the captain at the approach: An ATR slipped off the RWY just one day earlier, Rwy contamination and heavy rain at the time, known poor rwy conditions, knowing rwy has no shoulders at both ends, knowing one reverse was inoperative, knowing they were at the high end of the weight limit (plus the last minute jumpseaters), inexperinced crew (at training) in an airport that requires special qualification, and for TAM policy does not allow FOs to land (not even on good wheater), still unfamiliar with aircraft (boeing offspring)...
You are digressing from the fact that the airplane easily could have been stopped and would have stopped within the confines of the 6,365' wet pavement [as had numerous other A320s immediately prior to this accident] if only the operating captain in the left seat would have closed/retarded
both thrust levers during flare or touchdown. This "instinctive" elementary function of moving the levers to the idle detent position even applies to the fly-by-wire A320s where the thrust levers are "switches" . . . irrespective of whether one reverser is DMI'd, irrespective of whether it's raining or snowing, or whether the runway is short and wet.
The pilots screwed up perhaps due to lack of training, lack of experience, absent mindedness, incompetence. . . .