"I'm your new god, a better one. So you will bow down, and profess your love unto me, your Lord or I shall destroy you"
The minute the words were uttered from the misguided angel Castiel, God sat up and paid attention. Though harmless as Castiel may have been, the truth was there was no one left to protect him. Raphael? Dead. Gabriel? Murdered. Uriel? Destroyed. Anna? Ruined. The list went on and on, and though the tiny group of hunters the nearly insane creature claimed as his friends may have some say, it would not be enough.
Rather than challenging Castiel however, God took a different approach. Collecting anyone and everyone he considered good and kind, the highest angel took them right out of their timelines, and put them somewhere 'safe'. A small town called Silverlake. There, they were protected from Castiel's wrath, virtually undetectable from him in fact. That, however wasn't the only thing God did.
You see Silverlake wasn't just any town. It was a good town. There was no crime, no death, no evil, that had ever touched it or passed through to taint it. It was, virtually, a town of pure goodness and remained so throughout the centuries. It was there that the Winchesters would help train everyone that showed up whether they were seasoned hunters or not. You see, God wasn't just collecting people out of the goodness of his heart, he was raising an army. One that would, and could, stand up to the 'New God' and, quite possibly, defeat him.
Of course, you have a choice. Some didn't want to defuse the Angel, others wanted to destroy him completely, and some.... some wanted to stand with Castiel and have him rule.