Why have the later Middle Ages been seen as a time of calamity and crisis?

During the later Middle Ages, the last book of the New Testament, the book of Revelation, inspired thousands of sermons and hundreds of religious tracts. Revelation deals with visions of the end of the world, with disease, war, famine, and death — often called the “Four Horsemen of the Apocalypse” — triumphing everywhere. It is no wonder that this part of the Bible was so popular. Between 1300 and 1450 Europeans experienced a frightful series of shocks: climate change, economic decline, plague, war, social upheaval, and increased crime and violence. Death and preoccupation with death made the fourteenth century one of the most wrenching periods of history in Europe.