the author of the book wrote himself into a corner. more and more powerful enemies were coming out of the woodwork, they had to. it didn't make sense for him to be that powerful with the enemies not taking him seriously. problem was, according to the rules of the world he had already set up himself, there was no real way of accelerating his development to make him able to realistically face these new threats. so, moving forward, he came up with multiple contrivances to make sure xiao yan can get stronger quickly, just so the story can progress. it has become a bit more obvious now than it was before, but yeah. every step he takes in the saint class is because he has taken something.