Van Daniken published his first book, Chariots of the Gods
, at the same time he was being prosecuted for fraud in his failed attempt to get going in the tourist hotel business. He did a year in prison (out of three in the sentence) and used the proceeds from his book to pay his fines and repay his investors.
But van Danikan was the granddaddy of the rhetorical question book industry. So, for example, van Daniken basically says that if the designs on the plain of Nazca were not laid out from overhead, how was it done? Any number of idiots with genuine academic credentials have tried to show how it could have been done, including a NSF team who went to Peru to show how the natives could have built hot air baloons. No one looked at the obvious objection that even with modern technology, it would be a nightmare to attempt to do it with somebody flying overhead controling the men on the ground. The obvious answer to what van Danikan offers as a rhetorical question is that they used grid transfer. You draw a small version of your image, lay out a grid over it, then draw a huge grid on the site, and copy the contents of each "box" of the grid on to the large version. He also shows an image from a Mayan carving and asks what was for him a rhetoical question to the effect of "if this not an image of an ancient atronaut manipulating the controls in his spacecraft, what is it?" Well, that's same technique of the poofists in evolution threads who drone on about cosmic origins and the origin of life (which, of course, is not a concern for evolution), and take the line that if you can't explain it, they get to insert their imaginary friend superstition. Just because someone can't answer your rhetorical question of what the person in the image is doing does not mean that van Daniken's bullshit is true. (I have also read, but can't vouch for, a claim that van Daniken altered the image from the tracery of the engraing before publishing his book--keep in mind he was being prosecuted for fraud in another venture when the book was published.)
But as a publishing strategy to suck their hard-earned cash out the gullible, it was brilliant. In 1947, the United States Army Air Force was running a top secret project called Operation Moghul in which they released high altitude weather ballons trailing little, flimsy wooden boxes covered in metal foil. The point was to use them as passive radar detectors which would reflect Soviet radar signals, allowing the USAAF to identify their radar sites. I don't know if the project was successful, but in northwestern New Mexico, a farm caretaker found the wreckage of what was very likely a Project Moghul balloon, and reported it to the Army. Naturally, the Army immediately began a cover-up. It was a slow news day in what journalists call the silly season, and a reporter in Roswell, New Mexico published a story about flying saucers. The Army latched on to that, and began acting suspiciously in a ham-handed manner, and loudly denying that it was flying saucer wreckage, which makes a good deal of sense if they were trying to divert attention from Project Moghul. The story died away after a while, and was forgotten for 25 years.
But other scam artists had taken note of van Daniken's success, and in 1972, one of these jokers published a book about "the Roswell incident." They were off and running then, and it became a cottage industry in Roswell, which doesn't have much else in the way of tourist attractions. Naturally, if you pay them handsomely, people who lived in Roswell in the day are going to "remember" all sorts of things about government agents silencing people, etc. The wreckage was not found anywhere near Roswell, but they had a handle for their bullshit peddling, and the so-called Roswell incident has been making good money for those who prey on the gullible ever since. Just because no one in 1947 could explain the origin of the wreckage doesn't mean it was a crash site of a "flying saucer." Hilarity ensued and a lot of people have been making good money ever since.
It's appalling how the "History" channel goes in for bullshit like this, but it is unsurprising. They've got a bottom line to tend, and it's more important to them to attract an audience than it is to spend money producing shows which reliably recount actual history.
EDIT: I forgot to point out that the silly rhetorical question is an important feature of this type of television programming.