This would have been Ford’s view of the airport upon being cleared to land runway 20L:
The runway is labeled 20L. The taxiway he landed on is a dark strip to the left of the runway. It’s understandable and perhaps forgivable that he mistook the taxiway for runway 20L — they are both dark strips of pavement.
What in my mind is not forgivable is that he continued to land despite noticing a 737 taxi onto his “runway”:
You can see his Husky (small yellow plane) fly directly overhead an American 737 that is waiting to cross runway 20L. He even asked over the radio, “Was that airliner meant to be underneath me?”
Prudence dictates that if there’s anyone or anything on the runway that you don’t expect to be there, you go around, rather than risk a misunderstanding and a potential collision. Ford should have put in the power and gone around the moment he noticed that 737 taxi onto his “runway.”