Final answer:
Gregory became Pope by cultivating relationships with political leaders and expanding the Church's influence through missionary work, thus asserting the papacy's authority beyond mere spiritual leadership.
Step-by-step explanation:
After the death of Pope Pelagius II, Gregory became Pope in the context of a time when the authority of the papacy was not based on military power, and the position didn't signify spiritual leadership over the entire Church. Instead, popes like Gregory slowly asserted their authority by engaging with kings and overseeing the expansion of Christian missionary work. Specifically, Gregory the Great, who was pope at the turn of the seventh century, established his position by creating alliances with Germanic kings and spreading Christianity to gain trust and support, thus increasing the influence of the Church.
Pope Gregory the Great played a key role in developing papal independence by shrewdly balancing power among Germanic kings and using his spiritual authority for support. His actions set a precedent for the Church's influence beyond spiritual guidance, involving political alliances and missionary work critical to the expansion of Christian influence in Europe.