He had access to the back of the monitor. It was just mounted on a frame. He probably unplugged the input and plugged into the same port. https://www.wxii12.com/article/passenger-takes-over-airport-monitor-plays-video-game-while-waiting-for-flight/30573509
That's completely understandable.
Entirely. Asking him to leave, on the other hand ...
But it's an airport: the only reason anyone is there is to leave.
Or play a better game.
Should've asked if he had any extra controllers