Let’s be up front: the notion that the earth is flat is ludicrous. Anyone who believes this either is ignorant of the evidence, or simply wants to believe it more strongly than they care about evidence. A lot of people seem to think it has more to do with the former, but it almost certainly has more to do with the latter. This is because humans crave meaning-making mythologies, and the conspiracy cult of the flat earth offers just that.
Humans seem to be evolutionarily predisposed towards interest in what other people are doing, since this has allowed for the social cohesion that’s been instrumental to our survival. There is also an element that, the more other people there are who care what a particular person says and does, the more people will care what that particular person says and does, creating a positive feedback loop. Social status in the form of notability must have developed as a way of attaining reproductive access.