Who believes?

[K]

I always assumed dominion was just a reality-warping magical field that poured off Pretenders, and that this was the only difference between them and powerful magicians or beasts. The prayers of the faithful are a magic of their own and could be a catalyst or inhibitor of that field.

Winning the Dominion war is just getting your magical field to overpower everyone else's fields and solidify reality across the world into one form (where the winning pretender is the ultimate power).