What is the reason for the prosperity of Song poetry?

There are many reasons for the development of Song Ci. Poetry is the most developed literary world in the Tang and Five Dynasties in history, and its words are far less than poetry, leaving a broad space for Song people. Moreover, Ci has improved the deficiency that the sentence pattern of poetry is too rigorous and rigid, and the rhythm is too neat and monotonous. It uses all kinds of long and short sentences to express profound, delicate and rich emotions, so "to repair it, it can say what poetry can't say." In terms of subject matter, ci began as a poetic style of romance and gradually became a tradition. In addition, the development of urban economy also promoted the prosperity of ci.