Before the Zhou, China didn't even have a concept of heaven, or Tian, but they did have a high god called Shengdi. But the Zhou believed in Tian, and they were eager to portray the idea of heaven as eternal, so they ascribed the concept of the Mandate of Heaven back to a time even before the Shang, explaining that the Shang were able to conquer the Xia only because the Xia kings had lost the Mandate of Heaven. This, of course, would have been impossible, partly because the Xia kings had no concept of heaven, and partly because, as previously noted, they didn't exist, but let's just leave that aside. The Shu Jing is pretty specific about what caused the Xia kings to lose the Mandate, by the way, explaining, the attack on Xia may be traced to the orgies in Ming Tao. Sadly, the Shu Jing is woefully short on details of these orgies, but orgies are the kind of behavior that is not expected of a ruler, and therefore, heaven saw fit to come in, remove the Mandate, and allow the Shang to take power. But then the Shang lost the Mandate. Why?