I believe they are the same as the flat earthers. The pyramids have been examined ad nauseum and people still think that the giant masoleums were actually power generators or made by aliens, despite the fact that they each (at least the biggest ones) had vaults for the carcoghigi of a Pharoah and his queen.
If there truly are mile tall cylindrical chambered supports under them, it would stand to reason that they couldn't have been man made, and us likely the reason for this conspiracy theory, because aliens...
The cartoonist picture they illustrated to show their theory makes no sense.