Vicar Esta is in some ways a grand success story of the Church of Asmodeus's training methods, after a century of refinement post-apocalypse.
Esta didn't need to begin as excellent Asmodean raw material in order to end up a 6th-circle Asmodean cleric. He just needed WIS 18 and to be born in Cheliax.
Starting with a nearly arbitrary input student, the seminary takes in that raw material. It beats them into obeying orders about what to think, and finding it terrifying to think otherwise. It monitors their thoughts to make sure it worked.
With pleasingly reliable regularity, the seminary student obeys and forms a self-reinforcing Asmodean thought loop and gets Chosen. If it only worked half the time, Cheliax would search for better seminary training methods instead.
And what's really going on inside the new-made cleric? What deep things inside them, if any, are resonating with those thoughts they have been forced to think? Which exact fears and hopes are pinning any of those thoughts in place? Church doctrine below the level of Rugatonn says that it isn't important, and is a stupid question to ask, because who cares about all that stuff that nobody is allowed to talk about and that doesn't show up directly to Detect Thoughts. If you minimize its importance and tell everyone, above all the priests themselves, not to think about the matter or consider it important, then it will be unimportant and powerless.
It is one of several ways that the Church of Asmodeus has converged with LLM training methods.