Why did Mr. Lu Xun say that traditional thinking and writing methods have been broken since A Dream of Red Mansions came out?

In A Brief History of Chinese Novels, Mr. Lu Xun said: Although the whole book is nothing more than mixed feelings, traces of gathering and scattering, and accidental tasks, it is very different from previous human novels. ..... The narrative on the cover is true, and I have experienced everything I have heard, because it is realistic and fresh.

In other words, the root lies in the word "realism". The story of the novel is not made up by the author out of thin air, nor is it a distant historical past, but is experienced by himself. This is the creation of A Dream of Red Mansions, which started a new era of novels.