This is supposedly a conspiracy - involving virtually all the world's governments (certainly all of the industrialized countries) - to keep the flatness of the planet a secret. And the conspiracy MUST go back at least to the time of Christopher Columbus, if not long before him, including countries, governments, dynasties, etc., that no longer exist. In all that time, even with wars and economic calamities, not a single govt ever squealed. The Watergate Conspiracy involved only about two dozen men and within six months about half were tattling on the other half, but centuries roll by and nobody blabs about the flatness of the earth.
And when we ask about this, the usual explanation is that somehow MONEY IS INVOLVED. Who would pay off so many people - and why? The story is that NASA was set up (in 1958) to be a big boondoggle, maintain the fraud of the round earth, and let NASA people steal taxpayer money. Why set up a govt agency just so thousands of people could steal? I don't think there is enough money to go around that way. And look who's supposed to be paid to maintain the fraud - Scientists, people whose careers were intended to reveal truths not promote lies. Surely not all those scientists are crooked! And certainly a lot of scientists who support the Round Earth are not showing signs of being well paid!! Somehow this same thing is supposed to be going on in threadbare countries that definitely cannot afford to pay for non-necessary things.
If the earth were flat, that would suggest undiscovered lands - where The Edge is located - as well as possible resources over The Edge and down the Side. A lot of countries, and a lot of big investors, would gladly explore such territory ... if it existed. Nobody is even trying.