Why do you think people believe in a particular god? It’s because that’s the one that is familiar, that people believe in in that environment, right? But objectively, there is no reason to choose that one god or set of gods. Allah is not really more likely to exist than Thor. But if you don’t know anything about Thor, you are unlikely to start believing in him. In the same sense, there is objectively no reason to root for a particular sports team. People just do it because that’s what other people do in that environment. And, like with gods, you dont start rooting for foreign teams that noone else likes, even though they might have players on that team who are more deserving of victory.
The analogy is not about existance, its about peoples motive for believing smth. One belief is that it is good if a particular sports team wins, another is that a particular god exists.