Why was Xu Wei rated as the greatest literary theorist in the 6th century/kloc-0?

In the cultural history of Ming Dynasty, Xu Wei was a genius. He is good at literature, calligraphy, drama and painting, especially painting. He raised the traditional literati painting from spiritual connotation to artistic form to a new height, and created a school of freehand brushwork, with bold and unrestrained brushwork and great momentum. It has a far-reaching influence on China's paintings in later generations. The old man Qi Baishi once lamented: "The paintings of green vines, snow and great polyester can be vertical and horizontal, and I am extremely convinced. I wish I could not live to be 300 years old, or grind ink and paper for you. If you don't accept it, you will stay outside the door hungry. " "Ivy is a far embryo, and there is no talent in old age. Nine reasons to want to be a running dog, three doors to turn around "-Ivy is Xu Wei.