I think he literally doesn't care if what he says is true or false - he just opens his mouth and stuff comes out, with any relation between what he says and objective reality being a coincidence.
People who don't actually care about truthfullness are great liars because they feel no guilt about lying and have no tells at all when doing it that other people might subconscioulsy spot, since their bodies are reacting the same no matter what they're saying, true or false.
A lot of people in positions were lying is a common tool (such as politicians) have to train themselves to be able to lie without tells, but it comes naturally to Sociopaths, Psychopaths and Narcissists.