Stadium scene

You haven't been to a live game lately, have you?
There is a constant flow of people moving around inside, going to lavatories, buying food, gossiping, and outside there are people selling tickets, meeting other people, or leaving early.
Attention to the sport is much less than even 10 years ago. People are texting, taking pics and videos, in short ignoring what's going on on the field.
The pumps don't work 'cause the Vandals stole the handles
Bob Dylan

Actually, I regularly go to stadiums to watch sport. People inside, yes there would be a few (not in the number shown) but there would be nothing like that outside, not once the game had started.

The real implausible part is why in the world would they send Matt to such a busy place to get his go bag, especially since he had such a high profile target with him? It was a recipe for the inevitable disaster that ensued.