Tandem - thanks for your honest and forthright post.
For what it is worth, on the balance of probabilities I believe it was inadvertent IMC leading to CFIT. However I do not believe they simply forgot where the Mull was, blundered into a cloud and hit the hill.
I believe they were distracted sufficiently to momentarily loose the SA allowing the final flight path to occur.
Looking at the limited evidence available, I would hazard a guess that as the final flight path came IMMEDIATLEY after the very first waypoint change, that unfamiliarity, caused by a combination of poor training, lack of variant recency and possibly a misbehaving AP/Navaids/display was just enough to suck them both in and cause the event.
Reading yours, Jayteetos and Tucumsehs post and the official reports I think anyone looking coldly at the evidence might reasonably conclude the same.
It's easy to critise a crew for minor discrepancies that combine with other more sinister events to generate a serious incident or accident. I think we all make at least one such mistake each time we fly. It is also very easy to sit in an armchair and pontificate about limits. Especially weather!
However, if we were to critically analyse the minutiae of this flight, the crews apparent closure with clouds at high speed, not compliant with their required wx limits, must surely be considered. In my experience, this kind of non compliant act in an informed and generally compliant crew is nearly always related to experience. In this case experience on the variant. Over the sea it's not that easy to recognise just how fast you are going as the surface texture of the sea is infinitely variable and when the displays, controls and feel of the aircraft is unfamiliar the cues available to instinctively recognise when we are going too fast are degraded.
I think that assessment is fair, reasonable in the light of the evidence and most importantly highlights some serious inadequacies in the crews training and their subsequent management of the flight path.