Asking why he lied is like asking why the clouds rained on you. This is exactly the same mistake people make with Trump: you think he’s actually a human being who feels emotions and responds to them like the rest of us. But he’s really a sociopathic narcissist. They aren’t like us; they are purely driven by the drive for adulation and attention, and their lives as presented to us are fictional to the extent that they can get away with it.