Was it Han Fei, the successor and practitioner of Legalist theory, who proposed to Qin Shihuang to "burn books and bury Confucians"?

No, it’s Li Si.

Burning books to trap Confucians is also known as "burning poems and books to trap sorcerers (in one word, scholars are Confucian scholars)". After the Western Han Dynasty, it was also called "burning books to trap Confucians". Qin Shihuang burned books and killed "more than 460 people who violated the ban" in 213 BC and 212 BC.

The term "burning books and entrapping Confucians" comes from "Historical Records Volume 121 Biographies of Confucian Confucians", which states that "in the Ji Dynasty of Qin Dynasty, poems and books were burned and sorcerers were encircled, and the six arts were lacking from then on." What is often cited as evidence for the idea of ??"trashing Confucianism" is the words of Qin Shihuang's eldest son Fusu in "Historical Records: The Chronicles of Qin Shihuang" ("The world was first settled, and the head of Guizhou in the distance was not gathered. All living beings recited the Dharma of Confucius. Today, everyone attaches great importance to the rope of the Dharma. I am afraid that the world will be uneasy, so I can only go up to see it.") In the Preface to "Shangshu" written by Kong Anguo (the 10th descendant of Confucius) at the end of the Western Han Dynasty, it was also said: "When the first emperor of Qin destroyed the ancient books, burned books and harassed Confucian scholars, the world's scholars fled and dispersed." Liu Xiang of the Western Han Dynasty wrote in his "Preface to "Warring States Policy": "I accept punishment as a rule, and believe in small tricks as a way. Then I burned poems and books, and killed Confucian scholars."