Firstly you have to acknowledge the fact that the original fortifications made against the vikings were built on behalf of Charlemagne, back when his lands bordered modern Denmark after conquering the Saxons. East Francia had border fortifications against the Vikings, West Francia did not. Also according to my knowledge (I'm writing form the office where I do not have access to my books) the raiding fleets were getting larger by the size as the vikings realized it is better to circumvent the land fortifications and invade via sea. King Horik was the first to amass an organized invasion fleet, when he attacked Hamburg in 845 A.d. At the same time he sent a second attack fleet up the river Seine but it was turned back. After Horik's murder by a rival in 854 A.d. organized raids persisted for about half a century in Northern France. After suffering defeat in 878 A..d. in England, the vikings set their eyes on West Francia. The french managed to win in 881 at Saucourt, near the Somme River, but the Frankish king was killed and the victory led to nothing. After that West Francia did not have a powerful ruler to lead an army against the vikings. In 885 the vikings were besieging Paris. King Charles the Fat of the West Franks bought them off with a huge ransom but allowed them to pass by the city, whereupon the Vikings laid waste to the entire countryside for several more years. Nothing actually stopped this Viking invasion until 892, when pestilence so ravaged the army that they finally dispersed.

Also I would like to point out that East Francia only managed to subdue the Magyars 60 years later at the second battle of Lechfeld in 955 A.d. Until 894 A.d. the Magyars were switching their allegiances rapidly, fighting for the party who paid the bigger tribute. After invading and settling Pannonia the magyars defeated 3 Eastern Frank armied between 907 and 910 A.d.. They defeated the invading Bavarians near Brezalauspurc, destroying their army, successfully defending Hungary and laying Great Moravia, Germany, France and Italy open to Magyar raids. On 3 August 908 the Hungarians won the battle of Eisenach, Thuringia.Egino, Duke of Thuringia was killed, along with Burchard, Duke of Thuringia and Rudolf I, Bishop of Würzburg. The Magyars defeated Louis the Child's united Frankish Imperial Army at the first Battle of Lechfeld in 910. Hungarian raids continued all over Europe on a yearly basis. They suffered defeat at Merseburg in 933 A.d., but later managed to successfully raid as far as Reims to the west and Otranto to the south. By 955 A.d. the Hungarians raided Rome, Catalonia and pushed again into Italy to Apulia. Then, the second battle of Lechfeld happened which was a major victory to the East Franks/HRE. But this happened after western kingdoms successfully shifted to heavy cavalry tactics against the mass light cavalry warfare of the Hungarians. The end sum of recorded Hungarian raids varies from 45 to 47, from which only 8 were unsuccessful. So claiming East Francia managed to "defeat" the magyars is quite an exaggeration.