Sounds like this was exposure, but when I was in Iceland a few years ago our guide pointed out a tiny road that led to an out of the way tourist attraction (maybe this one) and said the local farmers were getting really pissed they kept having to haul out tourists in rental cars going where they shouldn’t and getting stuck.
I went to Iceland three years ago and did the brief drive on Highway 1....even stopping at the airplane wreckage site (they have a parking lot there for you). I’d take a guess that in a normal summer day, there’s at least 200 cars that stop there with tourists.
In this case? With no rental car in the parking lot apparently? I would suspect that the two were part of some tourist bus...given 30 minutes by the driver to take pictures and walk around...probably down some side path, and the bus pulls away. Evening came, and the two froze in the local conditions.