If Trump was not lying, he was bullsh*tting -- speaking with a reckless disregard for the truth; the moral equivalent of lying.   Reckless disregard for the truth is the defining characteristic of Trump's life.
In other posts, I've cited Harry G. Frankfurt's book, "On Bullsh*t" as a helpful way to understand Trump's pathological disregard for truth. Frankfurt distinguishes garden variety liar from a bullsh*tter.  Wikipedia summarizes the distinction this way: "The liar cares about the truth and attempts to hide it; the bullsh*tter doesn't care if what they say is true or false, but rather only cares whether or not their listener is persuaded." That's a perfect description of Trump: nothing he says means anything five minutes after he says it. Absent independent collaboration, nothing he says can be believed.
"Liar" is convenient shorthand for describing Trump, but "bullsh*tter" is more accurate. We probably need a word to express that concept that is not generally regarded as vulgar.