Patrick was a slave of the so-called "pagans, captured from Wales or South England. Having lived among them, he had a deep understanding of their beliefs. After escaping, converting to Catholic, he returned, adapted many of the "pagan" beliefs to make his brand of Catholicism acceptable to the general population. Sept leaders, by and large, allowed him the freedom to do so. A couple were even accepted into the Church. Patrick's beliefs differed greatly from the Roman Catholic church. At that time in history there were many differing ideas as to what constituted the "real, true Church." The were many so-called "pretenders" to the Roman centered church.
Years of this "pagan" converting by Patrick and those who came after him finally drove the Pope to distraction. He eventually issued a letter (a Papal Bull?) authorizing the English king to invade the Island and force it into the one true Church, Roman Catholic.
Irish history isn't easily understood without careful study.