I think y'all are setting different standards for what makes someone smart.
Yes, academically, he's a complete imbecile.
But what he lacks in mental aptitude he makes up for it with his sociopathic, narcissistic tendencies wherein he uses everyone for his personal gain and gets away with it by conning people into thinking he's smart.
As a society we don't often value traits like deceit so we think he's a moron, but let's face it, he's the master con-man. You have to give him credit for that, even if it's a terrible trait to have.