How? What do you think people think of him that’s untrue?

Since he first got seriously involved into politics I haven’t seen any evidence that he has a sophisticated understanding of anything, except two things: how to negotiate when he’s in a strong position to bully his counterparty, and pandering to his base.

Like a sibling comment points out, you refer to The Art of the Deal, but that was written entirely by his ghostwriter Tony Schwartz (according to both the author and the publisher). Schwartz has even said he thinks it should be recategorized as fiction.