On the contrary - I think it was a very windy day.
A witness on top of Ben More saw the last moments of
the aircraft’s flight but did not see or hear the impact.
He described the wind at the summit as “very strong”
and that when he removed an item of clothing from his
rucksack it was nearly “ripped” out of his hand by the
wind.
Over Scotland, the surface
wind observations valid at 1100 hrs UTC show westerly
winds of 10-15 kt with a 2,000 ft gradient wind of
310° at 25-28 kt. At Glen Ogle, near the crash site, the
surface wind between 1000 and 1200 UTC was westerly
16‑19 kt with gusts of 24-26 kt.
Was this data not available to the pilot, preflight? Form 214, etc.
I would think that a surface wind of 20kt is going to be 30-40kt at any altitude. It's one of the most basic rules in flight. And it veers to the right, etc, etc...
the isobars showed no such pattern. Local venturi effect of terrain and overlying air masses can have a massive effect on windspeed over high ground.
Mountains cannot make wind out of nothing, using some venturi effect. There has to be a general airflow, or updraughts by solar heating.