Destroying Caerwyn will not destroy Verdis Elementum. I'd dare say it'd only make it stronger, as the Caerwyn diaspora will bring their faith with them and convert the unaligned. After all, many of the realms I've spoken too were very interested in VE, but we just don't really have enough people to go spread the word to these parts of the world as we are mostly all busy with other stuff.
VE started with Caerwyn, and had little interest in beyond. I fetched it and made sure it became more than just that.