Why do people listen to Trump?

Donald Trump is a pathological liar who is physiologically incapable of telling the truth. The thing that surprises me the most is not so much anything about him as that the press still seems so shocked every time he lies. It's as if they still believe that he is suddenly going to start telling the truth just because he's president, or something. He very often says exactly the opposite of what he said previously, and sees absolutely no contradiction in doing so. For example, there are still lots of people in the media who seem surprised that Trump dictated that letter about his health that was supposedly written by his doctor. Anyone with half a brain should have been able to see that no doctor would've made the ridiculously absurd claims that were made in that letter. Okay, so I have to admit that I thought was that Trump paid off the doctor to write the letter, and not that the letter was actually dictated by Trump, but I was absolutely positively certain from the very beginning that any statements supposedly from medical professionals presented by Trump were nothing but a pack of lies, and it appears that I was correct in this. It should be clear by now to everyone that absolutely nothing that comes from Trump is the truth, and I simply can't understand why there are so many people out there still believe anything that Trump says.