Social Services: Many of the social services that are now offered by secular governments were once the exclusive domain of the Roman Catholic church. Only the Church could marry you, baptize you, or bury you. There were no passports or identity cards and so your baptismal certificate and parish records were your only official identity documents and proof of residence. Poor relief was handled exclusively by the church, as were hospitals and asylums for the poor.
Political Power: The Pope was not only a spiritual leader but the temporal head of the Papal States. The Pope's ability to excommunicate a king or noble gave great political power, as did the sheer wealth and influence of the church.