I cannot comprehend how a flat-earther can believe that there is some kind of conspiracy hiding the truth. There are literally millions of people that directly depend on a spherical earth in so many different ways. I can't fathom how so many people could keep such a secret for thousands of years.
I also find it hilarious that flat-earthers believe that Ptolemy got it wrong -- not because he believed that the Sun and planets revolve around the earth, but because even he knew that the earth is a sphere.