I’m surprised they chose the baggage claim area. People tend to be even more densely packed in while lining up for departures and you usually don’t have to undergo any screening to get into the initial check-in area for departures. Although some baggage claim areas can be accessed by the public, in many large airports (Toronto for example), non-passengers cannot enter the baggage claim area and there is a security official posted at the exit.
I think it depends on the airport. When you come out of the passport area in the international terminal in Madrid, for example, you go downstairs to the baggage claim area and you can then wheel your luggage cart right through a very wide door into the (non-secure) arrivals terminal, where there are crowds of people piled up waiting for friends and family, as well as limo drivers picking up tour groups or business travelers. I’d suspect this airport was designed similarly. Made to order for someone wanting to cause mayhem, unfortunately.