If there were no Viking raids on the monastery in Kilkenny (and there is no record of any,) it may have been due to the influence of Cerball* MacDunlainge, the powerful king of Ossory.
Ossory was the ancient state covering most of what is now County Kilkenny, and extending northward into modern-day County Laois.
Cerball's fame rests upon his interaction with the Vikings. He commanded a fierce army and was a great diplomat. Historians note his ability to create military alliances, arrange marriage treaties and to battle with whom he could not negotiate.
It is possible that during the period of inland Viking raiding, Cerball's kingdom of Ossory protected Kilkenny's monastery from attack.
The Vikings began to invade inland waterways about 25 years after their first accredited Irish raid in 794.
They first attacked Ossory in 823.
In 845, Cerball defeated Vikings in a battle at Carn Brammit. (These data are from the Annals of the Four Masters, the repository of Irish monastic scholarship. Nobody now knows where Carn Brammit was.)
In 856, Cerball made an alliance with Dublin Vikings against one of Ossory's neighbors.
In 860, Vikings attacked, and Ossory slaughtered them.
The list goes on. In the 60's and 70's, Cerball was the most powerful ruler in Leinster, the southeast region of the island.
When he died in 888, Cerball's heirs continued his legacy of battle and alliance.
By the early 870's, the powerful Dublin Vikings had begun to fight between themselves, politico-familial contests weakening their government from within.
In 902, the Irish expelled Viking leadership.
On their return in 914, the Vikings' behavior was different. There are records of monastic raids, but these may have been more political and warlike than the earlier booty-oriented attacks. Apparently the Kilkenny monastery did not merit punitive action during this last phase of Viking Ireland. (Or [still] did not allow it....)
The age of prominent Viking military-political influence in Ireland came to an end in 1014 at the battle of Clontarf.
It seems that while the Vikings were plundering inland, a strong Ossory made Kilkenny's monastery an unattractive target.
*"Cerball" is the Anglo-phonetic version of the Gaelic Cearbhall. "Ossory" is Anglicized Osraighe.