As for an answer to the title question,
His supporters are short- sighted and incapable of critical thinking. They hear he's going to punish those evil rich people and shower them with free stuff, and that's all they need to swear allegiance to him.
They have no knowledge of history, and thus have no clue how much of a failure Socialism has been everywhere it was implemented, and thus have no clue how devastating it would be in the long run if it were implemented here.