There are definitely trolls in the flat-earth community and I am pretty convinced that the majority of the 'famous' flat-earthers on Youtube are only doing it for the money. They are scam artists and their target is the myriad of scientifically illiterate people who genuinely believe their crap. Look at all the people who believe in unscientific ideas such as astrology, homeopathy, spiritism, power of crystals, ancient hidden civilizations, ... Add to that the bronze age cosmologies described by the holy books of most religions and you have the perfect environment to bring people to the border of the rabbit hole. Once they are there, Youtube provides the final kick to fall in the hole.
An important factor is the recent resurgence of creationism in the US and in most areas of the world where religious fundamentalists are thriving. Initially, the creationist movement was only targeting the Evolution Theory but all sciences are connected:
- The old ages of Earth and of the Universe are confirmed by Geology, Astrophysics, and Nuclear Physics (i.e. via Radiometric dating) so those sciences MUST be wrong.
- The common ancestry of all life forms is confirmed by DNA analysis, Paleontology and Anatomy so those sciences MUST be wrong.
- The Noah Flood is disproved by History, Geology, Climatology, DNA analysis so those sciences MUST be wrong.
- etc
The end result is that a fundamentalist preacher has no other choices than to denigrate all modern sciences to justify his bronze age beliefs.
Youtube and other social networks are not the cause of irrational beliefs but they provide a good environment to amplify them.