>>713640137
Miquella's failure is unrelated to getting rid of St. Trina.
The whole game hammers down that the Fingers and the Guidance of Grace are evil for meddling with and controlling people, binding them in a cycle of suffering and manipulating them in a world of endless strife.
Miquella wants for his Order to replace that. An age of control led by an absolutist God hellbent on controlling people by dulling their senses.
Ansbach literally describes Miquella's charm as a fog, similar to that which the Confessors use to deaggro enemy and make them unable to defend themselves.

St. Trina's abandonement was part of his cleansing, sacrificing his humanity and self as cleansing ritual.

The game acknowledged both the tragic sacrifices Miquella has to accept and the the terrible dystopia he will bring upon the world