While I've never personally used that word to ever describe him, he does in fact have a long and well established reputation (from the 80s & 90s) as being a liar, cheat, conman, bully, master manipulator, etc, which was well documented in many news articles published back then.
In one of those articles, Trump's own lawyer was quoted as saying "Donald is a believer in the big-lie theory. If you say something again and again, people will believe you."
Oh look, here's that September 1990 Vanity Fair article in which he's quoted saying such...
https://archive.vanityfair.com/article/share/e515a2cd-a51b-4f83-8d61-6ebb9a104e0a
Fast forward 32 years and he's still doing it with his BS claims of a stolen election. It's bad enough people are still suckered into believing him decades later due to not knowing his history but what's truly unforgiveable is that he tried to steal the election for himself due to egotistical need which ultimately led to an insurrection. That can NEVER be excused.