The Vikings have often been blamed for causing the breakup of the Frankish Carolingian Empire, but the driving force for this was internal and dynastic: the Vikings certainly profited from the empire's internal divisions but they did not cause them. Carolingian rulers did not regard the Vikings as being nearly as serious a threat as their dynastic rivals. However, the Franks did not share their rulers' priorities. They increasingly perceived royal countermeasures against the Vikings as half-hearted or even cowardly, and by demonstrating the ineffectiveness of royal power the Vikings probably hastened its decline. The most important long-term consequences of Viking activity in Francia was the establishment of of the duchy of Normandy, the importance of which to the future history of France, England and Italy can hardly be understated.
As in other areas of western Europe, Frankish monasteries - and their monks - suffered severely from Viking attacks, and many were abandoned. Monasteries were the main cultural centres of early medieval Europe, and the revival of learning fostered by Charlemagne, known as the 'Carolingian Renaissance', had collapsed before the end of the 9th century. Severe economic damage must also have been caused in the short term by Viking plundering both in the towns and the countryside. Wooden buildings were easily rebuilt, and the fertility of the soil could not be taken away, but losses of livestock, seedcorn and manpower would have caused years of hardship for peasant farmers. Two major towns, Quentovic and Dorestad were completely abandoned in the Viking Age, but the culprit here appears to be silting of the rivers that gave access to them, rather than Viking attacks. Some Frankish merchants saw the in the plunder-laden Vikings an opportunity and traded with them, though this could be a dangerous business: Franks who had entered a Viking fort in Flanders to trade in 882 were captured and ransomed. Overall, however, the Vikings do not seem to have had the stimulating impact on trade in Francia that they had in the British Isles. Nor did the Vikings have any cultural impact on Frankish civilization: even in Normandy, the Scandinavian settlers were quickly assimilated to the native population, leaving little trace of their presence behind.
Notes from Encyclopaedia of the Viking Age by John Haywood. Thames
& Hudson 2000. p76.