Anybody who is genuinely curious why Trump is doing so well in the polls, Scott Adams (Dilbert cartoonist, not a Trump supporter if you're worried about bias) has been blogging for months about his rhetorical strategies & why they are so effective:
http://blog.dilbert.com/tagged/Trump
some of the better ones imo
http://blog.dilbert.com/post/126589300371/clown-genius
http://blog.dilbert.com/post/128401835811/nice-guy-part-of-my-trump-persuasion-series
http://blog.dilbert.com/post/128709386661/a-demonstration-of-persuasion-part-of-my-trump
http://blog.dilbert.com/post/129215160011/why-trump-insults-people-part-of-my-trump
http://blog.dilbert.com/post/127793580186/trump-and-godwins-law
or TL;DR in Adams' words: "Does the boring candidate ever win? No."
Love him or hate him, the reality is that Trump is manhandling the media in the way that has possibly never been seen before in ANY country's elections. He might seem bumbling but I would hazard that every aspect of his public image is completely intentional. The usual political pundits and whatnot don't get it simply because they've never seen it before. You have to keep in mind that this man has been in the media for many many years, he understands public perception on a very deep level. Also worth noting that until some point in the 80s, Trump's public persona was much more subdued. It wasn't until he started clowning around with pro wrestlers that he became the loudmouth Trump we see today. That was surely intentional too.
An example - I doubt many of you watched the most recent Republican primary debate (I did, it was way too long and boring) - but for those who did, 90% of people will only remember one part: Jeb Bush telling Trump "you can't become president by insulting everybody" and Trump responding "I'm at 42% and you're at 3%, so tell me if it's working" or something along those lines.
edit: sorry I'm getting boring here, but another thing - if Trump was an idiot he would never be able to pull this off
poor Jeb...