In my CK2 game, I am playing as a Catholic republic (Venice - Carpathia Empire), but I deliberately have a Jewish vassal (Kingdom of Jerusalem). Initially all the temples were Jewish, but when the Rabbis died, all the incoming rulers flipped to Catholic Bishops, rather than staying as Jewish Rabbis. This happened with both free investiture and papal investiture. Counts, Dukes, and the King are all Jewish. Mayors are not flipping, only the Bishop/Rabbis.
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