Even though landing on a taxiway can't be justified I am sure they would have seen any aircraft taxiing. It was a mistake and they will pay dearly. I don't think it is career ending. You can bet they will never do it again.
Transisioning to the inner runways might have just one row of lights to the right instead of the other runway. Bad on them, wrong colored lights but they screwed up and am sure admitted it. They were tired and made a mistake. I quit doing the long hauls for that reason. Fatigue. I like daylight flying.