Mephis as I understand it, the early Jesuist christianity took its organisational structure directly from the pattern used by the earlier so called "pagan" religious cults. It would be appropriate to mention that they borrowed practically everything else including most doctrines, fables, imagery and ritual from the pagan christ cults as well.
In other words I think that the Gnostics were only one of many groups probably already using a traditional hierarchical ordering already of historical standing.
This included having a bishop (overseer) presbyters (older men) and deacons (lowly attendants to the material aspects of the church). As the numbers of believers for a particular cult grew then the importance of the management also grew and the bishop became the key man to make sure there was enough money to support both the welfare and feeding of the poor and the upkeep of the church building in a particular region.