My pretender died for no reason!

[ceremony]

Cainehill said:
because of the way temple checks work : with a starting dominion of 2, your temples will _never_ have more than a 20% chance of increasing/spreading dominion, regardless of your maximum dominion from building temples.

That actually isn't quite how it works: temple checks are based on maximum dominion, so building additional temples will increase your dominion spread chance.