Why did Christopher Columbus think he landed in the East Indies?

There is the myth that everyone up until the time of Christopher Columbus’s voyage believed that the earth was flat. However, astronomers, other scientists, and mariners were well aware that the earth was spherical. This could be seen by the movement of the heavenly bodies, the outline of the earth’s shadow during eclipses, and the descent and approach of the masts of ships as they traversed the horizon.
Europe, for centuries, had been involved in overland trade with India and the Far East. This was a long and arduous journey, and so it was hoped that ships could sail to the west and wind up in Asia and its outlying islands. However, no one knew how large the circumference of the world is or that there are two continents and a myriad of islands between Europe and Asia. Therefore, when Columbus set sail for the west and reached land, he assumed that he had arrived in the East Indies.