Jacob couldn't help but think about the Myth of Reverend because every clue pointed toward him, starting with the latter's sudden appearance and his instant acquisition of high authority within the Mythical Coalition.
After all, the Coalition Master had always been a mysterious figure and had never shown himself except in his cryptic appearance, according to the Myth of Black Archer's memories.
So, Jacob also thought that the Myth of Reverend wasn't the Coalition Master, since he was far too ambitious and seemed to have a purpose.
Moreover, the Myth of Reverend's obsession with the survivors of the Sagittarius Continent and quickly thought about the information on the Star Network, which pointed towards the Death Lord, someone who can use curse magic.
