I do not know how the aircraft in question was operated, but during my years on the F70/100, no RNAV approaches were permitted. While the FMS showed the relevant approaches inserted in the database, we were never certified to use them.
A non-precision approach, if handled correctly, is not less safe than an ILS or the like and by itself no reason at all to crash an aircraft. There have been aircraft flown into the ground on an ILS as well, see the
Alitalia DC-9 at LSZH in 1990 for example.
It will be interesting though to see whether the GPWS was serviceable and working on this flight.