It was a turf war: plain and simple. The independents had all been swallowed by the Big Three who were now each using the political influence they'd garnered along the way to try and crush the other two. The prize was total national dominance of the market, and a hefty slice of the action abroad where the product had been zealously pitched to a receptive customer base, building up a lucrative following among locals and ex-pats alike. The three sides had reached a stalemate, a state of perfect competition where no-one was able to out-manoeuvre the others in any practical way. All that was left was marketing. Three huge propaganda machines geared up and began staking their claims on monopoly.
We're in Ireland, by the way, and it's coming up on the year 700. Kildare is probably in the strongest position of the Big Three monasteries who control the church between them. It has a loyal following of smaller monasteries, a strategic position near the centre of the island and a clear pedigree going back to Brigid the first abbess. Their advertising copy was first out of the scriptorium: a Life of St Brigid which clearly stated that Kildare was Ireland's primary Church, the rightful mother-house of all the nation's religious institutions, with all the associated power, influence and revenue.
In terms of sheer political clout, however, Iona had primacy. Its worldly power was based on its founder St Columba: a clever aristocrat who, 150 years previously, could have ended up as one of Ireland's most important kings had he not entered religious life and established his monastery on the island. But its off-shore position was a weakness, and not even the well-placed daughter houses in Derry and Durrow could collectively wield the political influence it needed to overcome its rivals. The Iona marketing department's Life of St Columba had conscientiously downplayed the distance factor and put the case that this monastery and its founder had always attracted the loyalty of Ireland's secular powers, and should do so today as well.
And then there was Armagh. While long-established and built on a loyal power base beside Ulster's capital city, the monks of Armagh's Ministry of Truth had nothing. Nothing. They leafed aghast through the gratis copies of the founders' biographies sent gloatingly from Kildare and Iona. Though long dead, Brigid and Columba were still carving out a bigger piece of the pie for their monasteries, and Armagh needed to react. Fast. Except... no-one knew who the founder of Armagh was. There was no great legend told around the refectory fire of "St X of Armagh" being shown the site of the monastery by the angels; no story of how St X had converted the local pagan king to the Faith and been granted the lands, nay, the island, in perpetuity. The Irish kings would soon start believing the claims of Kildare and Iona that they had always been top dogs, and Armagh would be out of the race. Unless...
There was a shout from the bookstacks and one of the younger monks came rushing into the scriptorium with a slim volume. They were the writings of some long-forgotten missionary from Britain: mostly maudlin navel-gazing, sections plagiarised from St Paul, and more than a bit of borderline-racist commentary on the barbarous Irish he believed himself appointed to save. It was undated, it mentioned no recognisable placenames, and nothing about the founding of monasteries. To the propagandists, however, all that mattered was that it was old, and that its author, "Patricius", considered himself to be the first bringer of Christianity to Ireland. The scribes looked at each other across the table. It was a crazy idea, but it might just work...
In the flash of a quill, the Life of St Patrick was circulating alongside the rival biographies from the other monastic oligarchs. Of course, everyone already knew the history: the first Christian missionary to Ireland was Palladius, sent by Pope Celestine in 431. That was an established, unassailable fact. The new book out of Armagh didn't deny it, of course. But it said, for the first time, that Palladius wasn't up to the job and never actually reached Ireland, yes, and that Patrick, arriving just a year later in 432, was really the man single-handedly responsible for spreading the faith through Ireland. Bits of Patrick's own writings were interspersed to give a whiff of authenticity to the thing, but the main message had been cobbled together in Armagh just the previous week: Patrick was first; Patrick was best; and Patrick established his monastery in Armagh.
The politicians bought it. Hook, line and sinker. Soon tributes were pouring into Armagh and its daughter houses, and Kildare and Iona gave up the fight. Ireland had a single, central church for the first time -- headquartered in Armagh and based around the legends of its "patron saint" who was now, by extension, the patron saint of the whole island: St Patrick -- a man who had lived and died in utter obscurity during the last gasps of the Roman Empire, only to be figuratively disinterred over two centuries later to front a propaganda campaign for some power-hungry monks.
Cheers. Mine's an O'Hara's.