Where did those people under the Yellowstone Bridge go

The people under the Yellowstone Bridge didn't disappear, they were hidden in a mysterious place, which is the bridge hole under the Yellowstone Bridge. This bridge hole is in a hidden location and few people notice its existence. Those who jumped off the bridge actually utilized the characteristics of the bridge hole to enter this hidden space. In this underground world, there were many people residing, who had their own rules and order, their own social circles and ways of communication. The people in the bridge cavern lived a simple and self-sufficient life, they planted vegetables and raised poultry, obtaining the necessities of life through their own labor. At the same time, they have also established a perfect material exchange system to meet each other's needs by exchanging goods and services with each other. In addition to the basic needs of life, the people in the bridge caves also pay attention to education and cultural inheritance, and they have established schools and libraries to carry out a variety of educational and cultural activities.