“Interviews with 30 attendees revealed a pattern in the stories people told about how they came to be convinced that the Earth was not a large round rock spinning through space but a large flat disc doing much the same thing. Of the 30, all but one said they had not considered the Earth to be flat two years ago but changed their minds after watching videos promoting conspiracy theories on YouTube.”
Source : Study blames YouTube for rise in number of Flat Earthers | Science | The Guardian