Columbus believed the earth was round from reading the Bible. From the Bible:
Isaiah 40:22
"He sits enthroned above the circle of the earth, and its people are like grasshoppers. He stretches out the heavens like a canopy, and spreads them out like a tent to live in."
Job 26:10
"He has inscribed a circle on the surface of the waters at the boundary of light and darkness."
Ah! But to a Flat Earther, Isaiah and Job were talking about a circle (2D) instead of a sphere(3D). We could be living on a dinner plate instead of a billiard ball.
