This religion sprang up as the result of the visit of the Thirteenth Doctor and her "fam" to the planet. The locals started worshipping the "Good Doctor". However, in the course of time, they mistook Graham O'Brien to be this Good Doctor. They also took his words about indigenous loba being human's best friends too literally and used them to enslave all the loba.
Due to his high position, Mykados had access to the true historical account of the Thirteenth Doctor's visit to Lobos. Yet he continued to lie to his congregation and was vehemently anti-loba and mysoginistic.
When the Doctor, Graham, Ryan and Yaz appeared on the planet during his rule, he at first showed deference to Graham, whose single surviving photo he kept under lock and key. However, when Graham spoke against Mykados' order to cave in the mines and kill all the rebels within, Mykados did not hesitate to accuse the TARDIS crew of being charlatans and managed to capture the Doctor and Graham.
With the Doctor insisting she was the real "Good Doctor" and some of his soldiers doubting his decision to incarcerate someone they have been seeing in the Temple since childhood, Mykados decided to revive the old tradition of fights to the death, pitting the Doctor against the monstrous Tromos, a loba who was experimented on to make him stronger and use against the enemies of the temple but who became hard to control.
When the fight was interrupted by the rebels and Yaz who helped the Doctor escape, he gathered his whole congregation in the Temple, even letting women and loba in and was going to give them poisoned wine, in belief that the second appearance of Graham and the TARDIS meant the end of days as prophesied in the Book of Truths.
After this second murderous attempt was thwarted too and after the Doctor materialised her TARDIS around him to protect him from the wrath of Tromos, Mykados chose to drink the poisoned wine himself, rather than live in a world where men, women and loba all were equal. (PROSE: The Good Doctor)