As the western Roman empire fell the roads that were before responsability of the empire, became no man´s land, this meant that they were lost and they had no one to take care of them, the germanic Kingdoms claimed and conquer former Roman lands, and with no army to protect them, there was nothing the population of those given lands could do, and the Roman Catholic Church became a powerful force, the only thing that didn´t happend is the mongols invadin, because they actually invaded the eastern part of Europe between the 12th and 13th century.
