I personally don't think Trump is unintelligent per se. I think he's a man child who is easily upset and doesn't 'do detail'.
He's also apt to make statements that make no sense. Only a few days ago.
He tweeted:
//Being nice to Rocket Man hasn't worked in 25 years, why would it work now? Clinton failed, Bush failed, and Obama failed. I won't fail.//
Rocket Man is Kim Jong Un.
He has only led North Korea since 2011. Clinton and Bush never had a chance to be "nice" to him as he was only eight years old 25 years ago.