Conspiracy theories — like flat Earth — exists on a spectrum, from the fringe to the mainstream. Each of us has a different demarcation line where we divide the spectrum into the reasonable and the ridiculous.
Flat Earth lies on the extreme end of the spectrum. Anybody who believes in a flat Earth also has its demarcation line on the far extreme, too, and as a result, tends to believe all sorts of other conspiracy theories. However, less extreme conspiracy theorists might find flat Earth ridiculous. By learning how people can believe in a flat Earth, we can avoid believing other, baseless conspiracy theories.
The conspiracy spectrum diagram here is rough and subjective, but should closely resemble their actual extremeness.
Some conspiracy theories depend on another. For example, believing a flat Earth requires believing Moon landings were faked, but not the other way around. Some conspiracy theories are incompatible with one another. For example, some flat-Earthers claim UFOs are NASA’s creation and do not believe the UFO conspiracy theory, even if it lies in their reasonable territory. But, had they were exposed to UFO theory before hearing about flat Earth, they would be susceptible to believing it just the same. However, doublethink is prevalent in conspiracy theories, and it is not unusual that people hold two or more incompatible conspiracy theories.
All conspiracy theories involve believing — without sufficient evidence — that people are working together behind the scenes with sinister motives. Flat Earth is unique from other conspiracy theories in the way that it is easy to prove Earth is not flat from simple, direct observations that anyone can do themselves, without having to rely on third-party information. Yet, some people still believe in a flat Earth. By observing how people can believe in flat Earth, we can identify the same pattern that might lead us into believing another baseless conspiracy theory.