Usually because their life sucks, through some combination of the shitty societal things like corporate greed that effects us all, as well as their own failings, like not trying in school, being an asshole so they don't have freinds etc.

And instead of accepting they are somewhat responsible for their own life, putting in the emotional labour of Introspection, admitting their mistakes and working hard to correct them, they listen to the guy on the TV who tells them everything bad about their life is actually because of the liberals and the illegals and trans people, and if we can just stop them, then all their problems will be fixed and Trump is the guy that's going to stop them, so they worship Trump because that's easier than helping themselves.