The article states that it wasn't on their charts. Other than sonar, how else would they know? Think they deliberately smashed into the mountain?
If I recall correctly from a previous article, there are periodic updates to the charts and those updates did reflect either the object they hit, or the fact that the area was poorly documented.
However, because of the nature of the orders received, the captain/crew did not take the updates into consideration.
My memory is a little fuzzy, but I believe that the summary of the situation was that the captain/crew weren't acting recklessly, but had they followed procedure, the obstacle would have been avoided, or steps would have been taken to proceed more cautiously.