My guess is that they mistook the localizer array as the beginning of the runway, due to whiteout conditions. The approach lights for 05 are few and far between, but there are a few lights on the localizer array.
A possibility but my chart shows three white flashing lights on the approach centreline and one either side of the threshold. Difficult to mistake for the runway as the runway end lights are green and don’t flash.
As they were already on the ground when they went through the localiser (witness the aerial stuck in the nose), they’d have touched down short of the what they were interpreting as “runway” anyway.