Dramatic operatic theaters with human actors speaking in vernacular language was a favorite form of entertainment as well, and some of China’s best dramatic scripts were written then. Also two of the four novels that are generally considered China’s best literary classics were written in vernacular language then.
So though the Yuan Empire wasn’t ruled by Chinese, it was an era of some historically renowned dramatic playwrights and novelists who wrote in vernacular language.
It is thought that the operatic style of the shadow puppet dramas that entertained the courts influenced the development of the operatic theater style of the Yuan Dynasty.
The Yuan rulers were fabulously wealthy according to historical accounts. They had a vast empire and control of trade in Eurasia. For the royal courts or the rich people, refined music, sound effects and talented singers were employed for shadow plays.
The Yuan “Zaju” style of opera was similar to their shadow plays. Perhaps the playwrights adopted the plots and the features. There were exciting plots, elaborate costumes, refined music and singing, action, and dance that the Mongols enjoyed. The music of the Zaju operas was called Yuan Qu (元曲 Yuan Music). The language used wasn’t the Classical Language but the vernacular language, so that the theater might be enjoyed by everyone. After the Yuan Dynasty, the operatic style developed into the Painted Faces style of Chinese opera that was popular until modern times.