Why did the ancient Kanyu family have to match the mountains and rivers on the ground to Sanyuan when choosing their capital?

When the ancient Kanyu family chose the capital, the landscape of the mountains and rivers on the ground should also conform to Sanyuan. In addition to the organic view of nature playing a certain role, this approach also has the idea of ​​imperial power being granted by heaven or divine power. "What the Son of Man Needs to Know" says that the imperial capital and even the place where the emperor is respected must not be geographically huge before it. It must be in harmony with the Tianxing Yuan Bureau and the Zhongzhong Zhenglong King Qi, and then it can be established. For example, in Beijing, the Yanshan Mountain behind is like a canopy in the sky, the Yellow River winds in front like a royal ditch in the sky, the Taihang Mountains are on the right, the islands in the sea, the Liaodong Peninsula, and the Shandong Peninsula are guarding the left, the Central Plains is in the middle, and the Qinling Mountains and Dabie Mountains are in the south. It is a very ideal Feng Shui treasure land to form a wall in order to respond to the dynasty.