Rowbotham lectured for 20 odd years about the Earth being flat and he did fairly well for himself.
He lived back in the 1800's, where there was not as much proof of a flat earth as there was today. There was not that many people sailing (and seeing the famous "masts is visible before the rest of the ship")or flying around the world back then, or using GPS, or seeing many countries send rockets, sattelites and manned spaceflights into space, and there was not that much of a globalisation either. There was not that many big towers etc that could be used to see how the world curve first-hand.
Today you would get ANNIHILATED for saying something this stupid in public, and actually believing it.
(in before "The Conspiracy", "bendy light", "circum-navigation", "huge ice wall guarded by 600 men on snow-mobiles", "huge GPS-towers everywhere" etc etc)
And the only reason he did well, was because he was well-spoken and idiots actually believed him. No-one here is well-spoken (no-one answers questions or come up with sound theories and try to counter Round Earth "theories"). Its all just "its the conspiracy", "look out the window, the earth is flat", "read the faq noobs" etc. But ofcourse there will always be idiots that will believe anything and people make lots of money off of that. Scientology, the moon-landing-was-a-hoax, 9/11 etc