Something about this story doesn’t make sense. When you arrive Internationally your baggage is picked up in a different area than Domestic flights. You cannot leave the area without going through Customs and Immigration. This article suggests that airline personnel directed them to Domestic baggage claim to pick up luggage. How could their luggage be there without this being deliberate.
Excellent question. Perhaps airport security cameras will reveal “who” directed them, and some intrepid journalist will report.