It has something to do with the history of calligraphy.
The evolution of calligraphy generally refers to the evolution of calligraphy fonts. Generally speaking, the Wei-Jin period is not only the end of calligraphy style, but also the integration period of calligraphy techniques.
In the Jin Dynasty, people advocated elegance and quality in daily life, and pursued the beauty of moderation and simplicity in art. Calligraphers came forth in large numbers. The artistic taste of bamboo slips of more than two kings (Wang Xizhi and Wang Xianzhi) catered to the requirements of literati, and people increasingly realized that writing had aesthetic value.
Wang Xizhi, the most representative of the spirit of Wei and Jin Dynasties, is the most influential calligrapher in the history of calligraphy and is known as the "sage of calligraphy". Wang Xizhi's running script "Preface to Lanting" is known as "the best running script in the world", and critics say that his writing style is like a cloud and agile as a dragon. His son's "Ode to Luo Shen" is magnificent, creating a "broken style" and "a book", which is a great contribution in the history of calligraphy. With the help of Lu Ji, Wei Guan, Suo Jing, Wang Dao, Xie An and Liang Jian, Nanzong calligraphy flourished. Yang Xin, Qi, Xiao Ziyun and Chen of Liang in the Southern Song Dynasty were all his followers.
Simply put, the "rules" of calligraphy were formulated in the Wei and Jin Dynasties, and the "two kings" were the most prominent in the Wei and Jin Dynasties.
I hope it helps you.