Overheating is not a cause of death I would expect at 10,000+ feet in western CO in late November. Dang.
Even if the outdoor temperatures were in the 40’s, it would get very hot inside the car with engine and cabin heat running. Also possible is a carbon monoxide component, which was not announced by the media but likely present as well. BTW the resort is at 8,200 feet, not 10,000.