I don't know any details about this particular case, but in general an advisory service such as Medlink will make a diversion recommendation based on a combination of the airline's preferred diversion points operationally and the availability and suitability of local medical facilities. Even in serious medical cases it can sometimes be better to stay in the air for a little longer to reach a higher standard of medical care than just drop in to the nearest airport - the medical equipment on board most airlines and the high standard of cabin crew training can mean the unwell passenger has access to a higher standard of medical care on board than in some locations on the ground. As I said, this is not a comment on this specific case but a general observation in the light of hardhatter's question.