The Vultures waiting outside the stadium is so dumb

So they just planned to sit there day after day waiting and waiting till the day their community inside the stadium falls? But at the same time they're allowing them to go out on runs and bring back supplies so they can keep their community running? Huh?

It would make some sense if the Vultures surrounded the place and refused to let them leave and starved them out, but thats not the case, they clearly allow them to leave and bring back food/supplies, it makes no sense. Hows the place gonna collapse if they keep letting them go out to bring back supplies and food?

Also what do the Vultures really hope to gain if it does fall? They have no food, its very low if they do, they don't really have anything of much value. They're acting as if its a goldmine inside that stadium when all i see in it is dirt, some old makeshift housing with some curtains and a small garden.

Definitely not worth perching yourself outside it permanently waiting for the whole community to eventually fall which could take months or even years depending on how good they can keep it going.