It all goes back to how the human primitive base ego functions. From out of the base ego, which is basically a defense mechanism, springs the Tribal impulse. The negative offset side of the tribal impulse is to hate and fear those “others” that are different. Thus Trump’s xenophobe rant hit the bull’s eye when it came to the fear of “others” with his campaign leadoff that Mexicans are rapists and murders — folks who are out to steal your jobs and so we need to build a wall to hold them back — line of unreasoning.
Next the base ego both hates change and hates to be wrong (conservatism play upon this factor all the time), so once it has committed to some idea or decision, no matter what new facts are raised, the ego will holdfast to its initial position for dear life. It requires a rather sophisticated intellect to override one’s base ego and many average folks are simply deficient in this department (not necessarily IQ deficient, but emotionally deficient) thus a solid group of folks are pinned to Trump by their inflexible base ego of emotion. Simple.