Fall of the Roman Empire occurred in 476: waves of barbarian armies swept into europe and dismantled the civil structure of the empire.
we the benedictines don't like your teachings so leave
The Roman citizens needed and wanted a change to restore the chaos: Pope Gregory the Great, led the church from 590-604 bringing order to the chaos.
St.Benedict had already started his christianizing work before the Church realized to do it. Founded the Benedictine Order at Monte Cassino in 520; where monks went/created a network of monasteries in Europe.
Irish monks of Columbia views of organization didn’t suit the demand of a Europe that required an administrative style more akin to the proven success of the Roman Empire’s System; but the Benedictines didn’t approve their teachings, so they gradually replaced the monasteries.