Ah, so it all finally comes together.
As to the conversation at hand, what purpose would these world leaders have hundreds of years ago to create a nihilistic belief system? To what end is this degree of conspiracy even remotely worth it? What is so impactful about propagating such a belief system that it has convinced every major player involved in such scientific and political endevours to go along with it?
Also, to believe in a flat earth must also mean a fairly hefty re-definition of a great number of scientific observations and understandings about the nature of the universe; of gravity, mass, and the mechanics of galaxies and solar systems. To what degree do you deny hundreds of development of our scientific understanding of the universe? And for the things you do deny, what replaces these? Is there such thing as gravity in this world view? What is the cause for the sun and moon's motion? What of celestial bodies? What is at the edge, and why has nobody actually taken any sort of evidence of it or reported on it?
Even if one doubts what one is told by others, it seems only clear that the option to consider most likely to be truthful is that which makes the least amount of unexplained jumps in logic and overt assumptions (like thousands of people participating in what would amount to an essentially perfectly-kept conspiracy for vague reasons), and that which is constantly reinforced by evidence from various relatively unrelated parties (whether it be basically any government with a space program, the Felix Baumgartner jump, footage from extreme high altitude planes, to name but a tiny fraction).