Trump's most recent tweets about the Russian incitements, and the killings in Florida really illustrate what I've already come to believe. Most people who wish to lie do so by first looking at the accepted facts, then building a lie as best as they can on these as foundations. It may require twisting the accepted facts, distorting them, re-interpreting them, or carefully selecting them, but virtually always they fashion their lies on some core of reality to try to make the lies sound more plausible. And they try to design their lies to form a consistent story.
Trump is perhaps the first public figure I've ever seen who does not bother to attempt to do this. He simply says anything that comes to his head at that moment with no effort to base it on known reality. More frequent than not his lies are the absolute opposite of objective reality and are based on premises that no one of any with any knowledge of the subject believes, whatever their political leanings. Indeed his lies are typically self-contradictory so each fresh lie often completely contradicts a lie he told earlier that day.
The only analogy I can think of is restricted to 2 year olds who have yet to understand how to lie effectively.
"Did you eat that chocolate bar?"
"No, Daddy."
"Then why is there chocolate all over your lips and nose?"
"Um... A bad man came into our house, held me down and smeared it all over me, Daddy. And the candy bar grew wings and jumped on me. And there is no chocolate on my face."
What I can't decide is if Tump has mentally deteriorated so much that he doesn't realize that he is blathering, or if his life of wealth and power, followed by being elected to the Presidency, has convinced him subconciously that he is so important and that people defer to him so much there is simply no requirement for truth no matter how trivial or important the matter.