Sure but Mathurin was there first, and then everyone joined under him. Your process requires taking someone new, and placing that person above everyone else. That's typically not a very popular move.
True it's not easy to get people to accept submission to a higher authority, however I honestly think if that doesn't happen SA is done for. Right now it's almost exclusively devoted to in-fighting. It's impossible to mobilize anyone for anything. We run SA like a representative republic which is not a way any religion I can think of has ever been run.
If the church wont adopt Severina I'm more than happy to try and start a new religion with her. I had decent success turning the Church of Aaron into a respectably sized religion and that was while contending with the active hostility first of Path of the Paragons and then of Trinitism. I predict the old church will not put up any meaningful resistance to her because like I said it's almost impossible to mobilize them for any purpose. Under those circumstances I think no small number of SA nobles will end up joining "Severan Astroism".
