What is the term for someone deliberately making extremely unrealistic promises?
From Thesaurus.com;
Main Entry: con man
Part of Speech: noun
Definition: confidence man
Synonyms: bilker, bunco, cheater, clip artist, con artist, crook, deceiver, fleecer, flimflammer, fraud, hoser, hustler, mountebank, scam artist, scammer, shark, sharpie, smoothie, swindler
Source: Roget's New Millenniumâ„¢ Thesaurus, First Edition (v 1.3.1)
Copyright © 2006 by Lexico Publishing Group, LLC. All rights reserved.
{Edit : I don't think either Con Man or liar (pre-edit) applies because both denote intent, which I don't think is there, but you asked}