There's two possibilities - the promoters were simply venal, or they are true believers themselves. And maybe I'm giving them too much credit, but I think the second option is the closer to the truth.
Because if I were simply a con artist, I'd look at those slides and go, "That's clearly a museum exhibit. There's no way the ultra-powerful government Black Ops would put one of the most significant artifacts in human history in a cheap glass display case (along with other artifacts), with propped up paper labels identifying it. Even if they, for some reason, did so, the fact that someone took a snapshot from outside the case with a flash camera, clearly within the sight range of at least one other person (the lady in the blue suit on the far side of the case), makes me doubt that this is actually a top-secret facility. It's simply a snap someone took on their vacation at a local museum. It's so obvious, how would I ever convince people it was an alien in a top-secret laboratory?"
It's so obvious, I can't imagine a good con thinking anyone would fall for it, at least without an exit strategy. If it were a deliberate fake, I'd expect it to be more convincing. Which leaves the still incredible idea that these "researchers" were given these slides and thought that this was actually an alien, not the remains of an unfortunate toddler in a small museum.
Then people wonder why Ufology isn't treated as a serious field of study.