Hi there. This is wrong. Just... incredibly wrong.
People had known the earth was round for hundreds if not thousands of years before Columbus. They had even done the math and experiments to figure out it's size (and gotten pretty close to being right about it). You can't actually navigate long distances on Earth without that knowledge. So what made Columbus special? He did the math wrong and thought the earth was 1/3 the size it actually is. That's also why he thought he was in the Indies in spite of having traveled a fraction the distance it actually would take.
The reason no one had ever tried to make the trip before wasn't that they thought they would fall off, it was that they thought they would run out of supplies and die. Which is exactly what would have happened to Columbus if there hadn't been a massive continent for him to run into.