The larger parallax created by the PAPI lights being only 47' above ground, instead of 75' above ground may have been enough to obscure them from the pilots view. I don't think he ever saw the PAPI lights. If he'd seen the PAPI lights, he'd have seen the bad indication, and it would have cued him to go around. Instead, coming down fast out of the low clouds, he saw the runway, and it gives little indication other than where to aim. If anything, it said to him "I'm here. Put it on the tarmac". Of course, that doesn't excuse not going around, when he came down so fast and steep while approaching an unfamiliar runway, but it could be what happened. I think 9999 out of 10,000 times, in the same situation, the pilot would have made the right judgment and gone around, but the one time he didn't, it ended up being the final hole in the Swiss cheese. I think maybe not one or the other pilots being fatigued matters so much, but I think, maybe they both were fatigued, contributing to the poor judgment to go through with the landing. From what I read about these pilots, they may not have been the very best on type, but they were good, enthusiastic aviators and righteous human beings.