After some thought, I have to go with the others who suggest that the pilot(s) were not CAT-II current or certified. A nice ticket to have, but as noted, it is not often needed for routine, well planned biz jet operations.
My only question here is why they chose to hang around for an hour before diverting. In such a situation that seems like a huge waste of time and fuel. Given the aircraft's modest size/weight, suitable diversion airports should not be difficult to find.
