Pure speculation on my part, but looking at the Flight Aware track, I'm guessing they saw airport lights and called the field in sight, controller then cleared them for the visual and told them to contact tower. They did and being a sleepy airport with no other traffic, tower controller immediately cleared them to land without looking.
Thinking the airport lights they first saw were the intended airport, they became fixated and lined up and landed.
I can see it happening. It's that complacency thing that kicks our butts.