I think there's a few core reasons

Some people would act like him if given the opportunity, so they identify with him or think he'd give them opportunities

Some people just feel isolated and know the world is getting worse but not why, so they latch onto the guy giving easy answers and simple solutions

And some people are just drawn to the idea of fascism or authoritarianism, even if they don't realize what that entails

I'd put the self loathing in the first camp - many of them get through life through projection. They think everyone is like them