
The shady guy isnt the one who made her the temporary saint, he's the one going against the real goddess, making everyone continue to view her as a saint even after leticia arrived and took her power.
She isnt supposed to still be a saintess, right now, she's using nefarious ways to remain in power; originally she saw a prophecy, that's why everyone thought she was the saintess (the temp part wasnt mentioned/she didnt tell people it was temp, I assume)

She had to have known she was initially supposed to be temporary since she made a deal with that shady guy to extend her position as a saintess. But according to the shady dude, she didn't understand that she had to act a certain way to keep her role and keep the goddess happy. Plus the bitch is crazy and delusional.

She is the worse, but if you think about it, isn't this whole situation partly the goddess's fault? Like that shady guy said, it is quite cruel to give a young person an important/prestigious position, then turn around and say, "Oh by the way, you're just the temp./fake until the real one comes!"
I'm not blaming the goddess for Josephine's current attitude and personality, but this specific situation-where Leticia, the Principality(?), and others who aren't apart of the Holy Empire suffer extensively and unjustly-might have not happened if the goddess sent out the oracle/prophecy when or after Leticia is born.
Josephine may or may not have been such a great person, but after receiving that oracle about being a temp, I'm pretty sure her personality and attitude would have definitely changed, and she'd be singing a different tune!
I'm pretty sure that shady guy would have found another way to go against the goddess, or whatever his plan is, but at least Leticia and the others would not have suffered so, and might be able to unite and stop him.
Tbh, I don't see much point in a temporary Saintess; I guess it's a position that-for whatever reason-can't be left vacant and/or unattended to, but I still feel like this whole situation is kind of the goddess's fault.
I'm not sure if I missed it or if it hasn't been revealed yet, but why exactly does the Saintess hate Leticia? Based on what I saw in the chapter with the prophecies, it doesn't seem like she knows that Leticia is the real Saintess, so why does she treat her so badly?