I lolled when I saw it on the news.
They were harmless. So let security look better at what gaps they have left, and be happy that they were lucky this time.
It is people that are doing random things that you don't expect that will get through security.
Groups, ideologists etc are easier to track down, to prevent from coming in. Because they plan and are under some kind of scrutiny already. And often are groups bigger than just two persons.
A couple or an individual is harder. They leave no traces before they do what they want to do. It's random. It's only to be found in their heads. This couple was not going for a kill. So, no harm done. A thing to learn from by security.