If a local church/meeting house/synagogue/temple/mosque etc welcomes musicians and dancers along to take part in a religious service as part of a festival it's helping promte the festival.

That seems commonsense to me. And I wouldn't need to be a Christian/Jew/Hindu/Sikh/Buddhist or Muslim to see it that way.

Notting Hill Carnival typically has this kind of thing happening in all kinds of religious settings. Including very definitely the Catholic St Mary of the Angels, with a very popular Mas Mass. And not just popular among Catholics.

That's what festivals are supposed to be about, everybody joining in and contributing what they have to give.