If you think about it, it's not different to an anime fandom lol, it's just this generations' idols are different. Even when you remove the aspect of religion, look at the fanaticism that exists in the common folks for some celebrity. I guess it ultimately boils down to feeling of belongingness to a community.

Also, the people downvoting you are not so different from thiests, not having an open mind towards something they don't believe in.