Yea, they could have the way more ruled was by deception, they sold indulgences etc and held hell over the head of the kings, Religion was big during those times so the kings and the people took it very seriously. Like a poster above said the pope had the pope to galvanize people for a holy way aka the crusades.
Over time the Church accumulated wealth so that also help their influence , on top of black mailing leaders that would go to confessionals and tell all of their wrong doings. The suposse power to forgive sins etc was very influential over the people
Pope boniface said behold i am Caesar, The RCC was and is a continuation of Pagan Rome
Hence the Pope is crowned with a triple crown, as king of heaven and of earth and of the lower regions