The Secrets of the Amish
Did you know that the Amish are really descended from a race of aliens that came to Earth many, many years ago. They sought a simpler life away from the wars and conflict of their galaxy in turmoil. They came to this planet to settle down and live peaceably and simply. When they arrived they sampled human dna to alter their form and the "Pennsylvania-German" language that they speak is really just a dialect of the national language from their home world. The first Amish barns really cover up the landing sites of where their ships came. If you dig down deep enough, you'll find a treasure trove of alien technology.
What if it's really the Amish that control the world and they are reluctant to enter into the regular society for the fear that they will be unable to objectively shape the course of modern events. Perhaps those members of their culture that choose to step outside of the Amish way of life are trying to enter the world to have a more direct impact on it, but when they leave, the elders perform a special ceremony that wipes their memory of being part of such a powerful culture and they lead more normal lives.
Did you know that long ago the ancient Amish went war with the Vikings? At the time, the Amish boasted superior weapons of war, but the Vikings were so ferocious and their military tactics so brilliant that the technological superiority of the Amish could not withstand them for long. Indeed, it was a boast from the Amish that they were so much more advanced than the Vikings that set the war off in the first place. After a brutal defeat, which almost completely wiped the Amish from the globe, the Amish elders sought peace through surrender. As part of the agreement, the Vikings ruled that the Amish should forever be forbidden to advance technologically. Even today, Viking descendents, secreted through society, watch the Amish closely for fear that they might one day rise again and threaten the Viking way of life.