Flat earthers believe there is a conspiracy covering up the nature of the earth. They argue that NASA is simply created to help keep the conspiracy alive. If this was the case, then the conspiracy would involve potentially millions of people across the globe. Conspiracies tend to fall apart the more people you involve. The Watergate scandal involved a few dozen people and couldn't be kept secret from the public. Secrets are generally really hard to keep from the public. There are constant stories of people leaking sensitive information to the press on a regular basis. Even some who know the consequences of revealing classified or sensitive information do it anyway. A great example is Edward Snowden revealing the NSA surveillance program. There is no way multiple governments could keep such a secret. Countries struggle with climate or trade agreements let alone keeping the flat earth a secret. It would require too much enforcement of too many people. Besides, if the earth was truly flat, why would this need to be kept a secret? Anyways, If you want to be entertained, I encourage you to watch you tuber - jeranism