Why did Zhou Wenwang write the Book of Changes?

For divination. People in the Zhou Dynasty believed in gods and ghosts. Before they make a decision, they often decide their luck by divination. The Book of Changes originated in ancient times. It is said that Fu Xishi looked up at the sky and looked down at the ground to get gossip. The Book of Changes in Shennong era was Lianshan, and the Book of Changes in Huangdi era was called Gui Zang. During the Shang and Zhou Dynasties, King Wen interpreted sixty-four hexagrams, making it the Book of Changes. Later, during the Warring States Period, Confucius wrote Ten Wings, which was called the Book of Changes, but Lianshan and Guizang were lost. From then on, one is the Book of Changes.