2) During the change of dynasties, feudal warlords were ignorant of literature and ink, and were not polite to ancient books and cultural relics. They even killed the literati together, let alone rebelled against the peasants. Every social unrest is more destructive. For example, during the Jian 'an period of Emperor Xian of Han Dynasty, the royal books and classics collected in 422 years of Han Dynasty (202-220 BC) were spectacular, but they were destroyed by turmoil, and the most feared thing for classics and literature was turmoil. For another example, a large number of ancient books before the Tang Dynasty recorded in Sui Shu's Jing Ji Zhi disappeared with Huang Chao's occupation of Chang 'an.
3) The biggest cultural disaster in China should be in the late Ming Dynasty, of course, due to Li Zicheng's occupation of Beijing. Most of the cultural tourism landscapes you see, such as Yueyang Tower, Confucius Temple, Wuhou Temple, Emei Temple, Mount Tai Dongyue Temple and Fengchan Terrace, were rebuilt in the Qing Dynasty, and most of the original buildings were taken care of by their own brothers. As for the existing cultural attractions, they were basically rebuilt in the 1980s, and the contribution of the Cultural Revolution to breaking capitalism is another story.
4) Finally, I have to mention Eight-Nation Alliance's war of aggression against China, which is an unprecedented cultural destruction. But then someone came. It's almost a three-dimensional carpet damage. Westerners certainly don't understand the value and national heritage of China's ancient books and cultural relics. As Wade said, "The details of the losses suffered by Beijing this time will never be found out." Yes, we don't know how many China cultural relics and ancient books have been robbed by foreign devils!