Why did Fu after An Shi Rebellion fall into the category of prosperous Tang Dynasty?

This is divided by specific historical characteristics.

After the Anshi Rebellion, all the poets in the prosperous Tang Dynasty fled Kyoto with the immigrants in the war, and some of them were trapped in the enemy camp because they failed to escape, so they had to stay in the capital. Some poets were forced to assume pseudo-posts, such as Wang Wei, Chu Guangxi, Li Hua and Du Fu. Under the imprisonment of the rebels, these poets passively formed a creative center.

In the days when thieves were trapped, the poet witnessed the desolate capital burned by the rebels. It is hard for them to believe the changes that took place in the Tang Dynasty in an instant, and it is also difficult for them to accept the status of prisoners and bear the great pain of losing their country. In addition, being forced to work in the rebels made them suffer from inner condemnation and conscience torture. Under the double pain of national decline and humiliation, most of the poets' works in the prosperous Tang Dynasty during the occupation of both capitals showed sad mood, showing the unique content and artistic characteristics of the poems of trapped thieves.