Why would sailors ever have believed that the earth was flat?
There seems to be a misconception that all people thought it was flat until Chris Columbus sailed the ocean blue. It was a superstition held by people who didn’t have the capacity for putting on thought after another. Much like those who hear one argument in favour of the moon landing hoax, but then fail to give it the few seconds’ thought that would make them realise that what they heard, whatever it was, is ridiculous. If they could see the edge of the world, it didn’t occur to them that the far-off Canary Islands, which they knew existed, couldn’t be see from where they were. It just isn’t some people’s habit to think “if . . . then . . .”.