Hmmm, I would presume the whole idea of flying to that particular location was to have a close look at the terrain, for everyones enjoyment and education.
So, one has to ask, if for any reason the flight crew where in any way unsure of their position and were also unable to keep the terrain clearly in sight, why then did they descend below the safe sector altitude?
Even if the crew were to have clearly trusted their navigation equipment, and felt sure it was correct, why descend below the sector altitude when you cannot clearly see the terrain, if that was the whole idea to begin with?
Sounds to me as though the crew is truly responsible for this very unfortunate accident.