Why did King Wen change the eight diagrams into sixty-four hexagrams? What's the motive?

It is said that Fuxi wrote eight diagrams to symbolize everything in the universe according to the river map and Luo Shu. These eight diagrams are dry divination, Kun divination, shock divination, Yi divination, deviation divination, Kan divination, Gen divination and exchange divination, and they are also the original and primitive forms of the Book of Changes. However, the universe is all-encompassing, nature is changing rapidly, and all causes and effects in the world are complicated. It is difficult to explain all this in detail and completely by gossip alone. Therefore, Zhou Wenwang combined with the actual situation, overlapping the eight diagrams in pairs, and thus deduced the sixty-four hexagrams.