how on earth did this all go so wrong?
Pretty simple really.
They shot a difficult non precision approach at high DA to a field with a deceptive sight picture (due gradient) and no horizon reference (due mountains) in a type apparently completely new to him with a 30Kt tailwind & reported 20Kt windshear on approach and a touchdown tailwind that was approaching double the type's limit.
What else would you expect the result to be?
How on earth were these guys allowed anywhere near an aeroplane in the first place is perhaps a better question.