If you watch him critically, you'd see there's more depth than the cartoon character that you typically see. I don't agree with his politics and methods... but he isn't some bumpkin. He is genuine in his fakeness.

Supporters hear the (real) problems he describes and a commitment to fix it. The details are where it breaks down.

Many public people who are good at what they do are amazing at flattening complex problems and making people understand and agree. Bill Clinton in his prime was capable of that -- he had a Steve Jobs like magnetic force.

If you look at some of more right-wing political people, many of them lack charisma, but use speech and body language techniques that are taught to evangelical pastors and others and are really effective in those audiences, but come off creepy to others. Kinda like how Mormons are awesome telemarketers because of skills acquired on missionary work.