The primary issue seemed to be raising the money, and this was covered by a business plan at least to some degree of detail.
This would be more convincing as a planning fallacy if they had raised the necessary money.
Otherwise, it's just: 'we will fail utterly if we do not get X; we did not get X; we failed utterly.' Is that so?
I think this should be read in conjunction with Peter Thiel's essay about stagnating innovation, where he talks about how society views technological progress. What I think Thiel misses is just how much the sense of progress was driven by a misestimation of the engineering--not to mention social--challenges to the future envisioned at mid century. The Artemis Project seems like an example of this sort of thinking.
I've been accused, rather angrily, of being unimaginative, but I feel like overactive imagination killed people's love of progress and so I have a duty to offer plausible near futures and pour some cold water on overactive imaginings.
I can't help thinking of these guys every now and then, with their nifty ideas like ascending from the moon with the astronaut sitting on a rocket motor in his spacesuit with no spacecraft needed.
Planning fallacy may have occurred here but this sounds a lot like people who just didn't appreciate the engineering difficulties involved. Orbital rendezvous is really tough. Some of the toughest parts of the Apollo and Gemini programs were trying to get that happen reliably. And if anything goes wrong, the astronaut only has their little space suit to protect them with whatever resources are on it before they can land again or attempt another rendezvous. This would be an extremely high risk method with a lot of engineering difficulties.
So, in order to go to the moon, they had to do all of these things right:
They had to get enough money, preferably with enough extra to deal with unforeseen budget overruns.
They had to design the hardware, correctly, on the first try. This is a lot harder than it sounds.
They had to build the hardware, and get the operations aspects worked out.
Oh, and then they actually had to go to the moon. Let's not overlook that particular challenge.
This is awful lot of things that have to go right. If any one of these fails, they're screwed. This is not how you do practical engineering if you actually want to succeed.
It's interesting to contrast them with SpaceX, whose plan was to start small, expect some failures, and gradually climb up the mountain instead of trying to reach the summit in one giant leap. They actually managed to reach orbit, and have a pretty promising future ahead of them.
Back in the 1990s I came across a site describing a plan for returning to the moon via privately funded enterprise. They presented a Reference Mission, a timeline (raise some money now, design the hardware, build the hardware, hire a launch vehicle, get to the moon, sell the movie rights) which had them starting to build hardware in a few years and touching down on the moon only a few years later. I even met one of the enthusiasts.
What I found interesting at the time was a presentation of the "Frequently Raised Objections" and their counter arguments. Their viewpoint was "we've got this completely solved--we're going!" The primary issue seemed to be raising the money, and this was covered by a business plan at least to some degree of detail. Of particular relevance was "It's all on paper, nothing is real". Wow, take that Mr Frequently Raised Objection.
Most of their points looked fairly reasonable in isolation, but of course the idea has failed completely. No launch, no hardware, and very little money. High confidence in the business plan despite little supporting evidence seems to have been the major problem.
I can't help thinking of these guys every now and then, with their nifty ideas like ascending from the moon with the astronaut sitting on a rocket motor in his spacesuit with no spacecraft needed. I guess the detail made the Planning Fallacy seem less likely at the time.
The parallels with some other ventures are striking.