I would presume that The close of the Viking Age (c. 800-1050) had less to do with the Norman conquests of England (1066) than the Christianization of Scandinavia (c. 975-1160).
It had everything to do with the Vikings themselves having risen to power in a lot of spots in Europe. William I was had Scandinavian ancestry and his conquest of England endured (the House of Normandy and the Plantagenet dynasty that followed were all Wm's descendants, give or take some whoring around by their moms).
In western Europe, standing armies that were well equipped, well trained, and well led had become the rule rather than the exception. Hardraada's death at Stamford Bridge marked the end of centuries of continual Scandinavian incursions in the British Isles.
In Sicily, the Normans drove out the muzzies, and their kingdom was set up with the blessing of one of the (anti-)Popes. The other Pope wanted the territory for himself, and brought in a couple of greater powers to destroy it. He managed to get it roughed up, and partly dismantled, but he never gained territory. Evenutally the Pope was captured and compelled to recognize the Norman dynasty and sign a treaty.
Later the Norman Sicilians conquered part of what is now Libya.
In the east, there was a Norman Crusader principality with a capital in Antioch. The Crusaders and the Armenians created buffer states that extended the existence of the Byzantine (eastern Roman) Empire, but of course along came a Byzantine idiot who thought it made more sense to destroy the Armenian capital and kingdom, helping to usher in the fall of Constantinople within a century. All those underground towns in Anatolia either appeared or were rehab'ed during that period of insecurity.