He attracts the lowest common denominator. His low brow but excessively loud humor attracts children, because his over the top reactions to most things resonate with people in such a way that they think he's "just like us".
He seems like a pretty alright dude in my opinion. Outside of his fake "Youtube persona", he seems like a pretty affeble fellow, I just don't like his videos because it's clearly so forced. If you can exploit the masses for hundreds of thousands of bucks a year, why not? I'd do it.