It's a terrible mistake to think that way. 62M Americans couldn't spot the con in 2016 & some of them still can't see it today. Just because we can see through it doesn't mean it doesn't work on other people. He might be the greatest con artist who ever lived.
I think it's hard to say if Trump is a calculating and cunning con-artist, or if he just happens to be horribly dysfunctional in the way that fits the dysfunction of the country and the political system.
I think it's the latter. It's like evolution - a species doesn't consciously and cleverly _choose_ to mutate in the way that suits the environment, rather the right kind of mutation is selected for by that environment. The current political environment has selected for the particular kind of personality flaw that Trump happens to have. I don't think he's doing it out of a kind of malevolent brilliance, I don't think he could do anything other than what he does, because that's his nature.