The residents in Vault 3 had refused to come outside after the stipulated 25 years established by the government.
No, we don't want to come out, they announced, and so the vault was kept locked far longer than anyone had planned it to. And it was for the best, as dangers did roam the outside world.
They regulated activities peacefully, their elected leaders coherent, level-headed people, and everything would have continued smoothly had the pipes not cracked down.
How could they remain inside when their living quarters were filling with water?
Don't let us out, they had demanded, and they had been right to ask for isolation. It was safe to remain inside. But the leak had happened, and there was no way around it any longer.
Cautiously, they had opened the door.
For a while, it had not been so bad.
They had traded peacefully and lived in relative calm, but it was their inhabitants being used to coherence and peace that kept them from protecting themselves from potential enemies.
The Fiends had taken over this territory, ruining a once peaceful, functioning vault, one of the few where life wasn't hellish.
Now, Vault 3 was just like any other place in this God-forsaken earth. Too bad about those faulty pipes.