I agree with Flipster, there are too many unknowns to find the guys negligent in any way. The west coast of Scotland is littered with aircraft that did not mean to fly into the ground. There are lots of contributory factors but no one will know exactly what happened on that fateful day.
I can add to what I perceive as contributory factors and describe how I tried to break the chain of possible events.
For me speed was definitely a contributory factor but groundspeed rather than airspeed; apparently there was a strong westerly that day that would have amplified other factors (next point).
Having spent a lot of time flying around the coast (SAR Boy) I know that it is sometimes difficult to judge how far away from land you are - if you see a sheep it is easy to judge because you know how big sheep are but quite often it is difficult to judge the size of rocks as they vary in size and they are quite big around the Mull. A similar effect can be found over the boulder fields in the Falklands - they vary in size making it difficult to judge height at low level. The rate of closure with the coast and the poor viz and low cloud would have amplified this effect and could have led to misjudgement by the crew.
A year before the accident I got a lift on a Wokka to Stanley from MPA for a function (p**** up). The weather was poor and we followed the road at low level. The Chinooks rarely went to Stanley at that time but the SAR Boys went to the hospital frequently. I was listening in the back but couldn't speak as I didn't have an interrupter and had disconnected my boom mic. I became uneasy as we approached the LS as I knew there were some large masts between us and it and the co-pilot (a Nav) had not mentioned them. I was trying to reconnect my mic to warn them when the aircraft turned 90 degrees right in quick time to avoid the masts. That was my first experience of GPS, reletively new at that time and not yet fitted to the SK. That crew had put so much reliance on the accuracy of the GPS without reference to a map that the aircraft almost crashed. I spoke with the crew about it and we all went away a little wiser but the bottom line is always navigate with reference to a map.
You may have read these points and thought they were negative but they are not meant that way - the bottom line is that the aircraft crashed into the ground and no one knows why but we can all discuss factors that may have contributed so that it hopefully will not happen again. I've had some near misses in my time and feel lucky to be still here to learn from those experiences but those guys were not so lucky and do not deserve to be blamed for something that they may or may not have contributed too.