The most likely theory is that 'Kami-dera' first existed as a place of ascetic practice for monks, following which the Shimo-dera was founded by FUJIWARA no Nobuko who had become devoted to Keiun.
先に僧侶の修行場としてすでに「上寺」があり、その後恵運に帰依した順子によって下寺が建立されたという説が有力である。