Because they only hear what they what to hear.
Their minds are closed to any further input – good or bad. One can argue with them until they’re blue in the face, but it will be to no avail. They’re deaf to his lies. They can’t see that he sows nothing but fear and discord. They twist his actions to make them appear as “beneficial” even though many are harmful or useless. To them, his hatred is love; his narcissism is strength and humility. To them, his slander and racism is 100% American. He is like a god to them, infallible. When he speaks, their minds only hear what they want to hear.
Shuhak 