I wonder how many offshore pilots have never landed on the wrong deck during their carrier ? .... as HC has said above, many contributory factors put together, make this mistake understable to those who really know the job. It's a bit like a gear up landing on fixed wings (and helicopters sometimes!)
The last barrier being the name reading on the hull or deck, it is not always visible or clear depending the approach configuration and the time of of the day (was it 7pm in this case ?)