"Losing Reality: on Cults, Cultism, and the Mindset of Political and Religious Zealotry," by R. J. Lifton.
What makes people turn over their minds to the control of others and become a zealot? This book is a collection of excerpts from psychiatrist Robert Jay Lifton. He has studied leaders, "mental predators," from Mao to Trump, and the ways they have sought to control the minds of others.
If time is short, just read the introduction: "on the ownership of reality." Here Lifton discusses one particularly fascinating aspect of cultic thinking: "Apocalypticism." That is, "end-of-the-world visions, of apocalypse in the service of all-encompassing purification. That sense of apocalypse turns out to be present in extremist political movements no less than in extremist religious cults." To me, MAGA, the slogan "make America great again", seems like the promise of purification.
Better reviews than I'm capable of are online.