Providing Top cover isn't exactly something that would be considered 'High Risk' operation. At least beyond the fact that at night over unlit sea (apart from the Lighthouses) is always a somewhat increased risk environment. But for such an experienced crew and capable machine that shouldn't be anywhere near High Risk.
Doesn't rule out CFIT but it is not a natural conclusion given the circumstances.
But, it hadn't got to that stage in the mission - it was planning to refuel at Blacksod before proceeding on task, any reference to 'top cover' is largely irrelevant in the specific context of the accident scenario (outside of discussion about the aircraft being airborne at all).