Oh, but they did.
Trump has been spewing out his plans for 10 years. His inability to understand complex situations, lack of world knowledge, ignorance of history.
The voters knew exactly what they were voting for.
Just like economics has been found to have far from rational actors, it's clear that there are millions of "low information voters". Many of them likely voted for him because he's that actor on tv who entertains them.
But yes, plenty of his voters heard what he had to say and liked it.
Tangent: in the United States, more people believe in angels than in evolution (69% vs 60%).
The voters knew exactly what they were voting for.