The problem with all the conspiracy motivations that have been offered up is that they're all circular. You can say the motivation is money, but no one was making any money prior to the conspiracy existing. The conspiracy needs to be in place first for someone to then exploit it and make money out of it. The fact that people don't know the earth is flat isn't (in and of itself) lucrative. The idea that someone in Ancient Greece decided to start a conspiracy that would be incredibly complex and expensive to run - on the impetus that when satellites and air travel become big business in two thousand odd years his ancestors would make a ton of money - is problematic at best.
Centrally - there's no real ideology behind the conspiracy. No one's given or shown me a deeper reason for why anyone would devote their lives to it. When the first conspirators discovered that, much to everyone's ignorance, that the earth really was flat, what was it about this truth that drove them to such incredible lengths so as to deceive the entire world for thousands of years to come? Nothing even approaching this scale has ever been achieved without it have some real deeper meaning to a lot of people, and so far, no one's given me even a theoretical example of what this might be.