That's a bit harsh, he's not lying, he's....selling. And, I would argue he may have been selling something he thought was indeed possible if not already in existence. Let's remember, DeLong has no collage background that I'm aware of, he spent most of his life as a musician. Not at all saying he's dumb, just that he, like me and lot's of people, may not have the physics chops to completely understand if ZPE is a thing or not.
More importantly, at the time of the emails, DeLong was in contact with at least 1 PhD level physicists and probably 2. DeLong co-founded TTSA with Jim Semivan and Hal Puthoff. Puthoff is a physicist and his long time collaborator and side-kick, Eric Davis, is also a physicist.
Davis and Puthoff were also involved in Bigelow's various endeavors like NIDS and BAASS. Puthoff's EarthTech company was contracted by BAASS to provide papers on possible future tech to fulfill the contract to the government run AAWSAP. Puthoff wrote a paper on space-time modification, while Davis wrote a paper on anti-gravity, something else DeLong often mentioned, and he wrote a paper on...Vacuum Energy otherwise known as Zero Point Energy. From the list of DIRDs (the official name for the papers they and others wrote):
There is no doubt that TTSA turned into a bit of a hustle and DeLong stood to gain financially from it. And it is clear that DeLong, both in the McCasland emails and other instances, including TJR show, made lots of hyped up claims in a likely attempt to make TTSA more legitimate. But I think it's also likely that DeLong had 2 PhD level physicists priming him about things like anit-gravity and Zero Point Energy. In his mind these are guys that had worked for the CIA, the DoD and had top secret clearance. Davis had written, and sold, papers to the USAF detailing teleportation and only a few years before DeLong was hyping TTSA in emails, Davis had written a government sponsored official DIRD papers on ZPE (Vacuum Energy).
DeLong may have well believed ZPE was real, or at least eminently possible. So, not lying, just selling something he thought could be real.