Why did Columbus believe that a western route to the Indies would be faster?

Christopher Columbus believed that a western route to the Indies would be faster due to a combination of factors that include his misinterpretation of the size of the Earth, lack of knowledge about the existence of the American continents, and his ambition to find a more direct trade route to Asia.

1. Size of the Earth: Columbus had read works by earlier scholars and geographers, such as Ptolemy and Marinus of Tyre, who had estimated the Earth's size. But he chose to adopt the most optimistic (smallest) estimates of the Earth's circumference. Because of these smaller estimates, Columbus thought that the distance between Europe and the East Indies (Asia) by sailing westward was shorter than it actually was.

2. Lack of Knowledge About the Americas: In Columbus's time, the Americas were not known to Europeans. The existence of this vast landmass, which lies between Europe and Asia if one is travelling westward from Europe, was not anticipated. Columbus believed that by sailing west, he would reach Asia (the Indies) without encountering any significant landmass.

3. Faster Trade Route: At the time, the known eastern routes to Asia were long and dangerous, going either overland through the Middle East or by sea around Africa—both were controlled by other European powers or by various Asian or Middle Eastern empires. Columbus believed that finding a direct western sea route would allow Spain to enter the lucrative spice trade more quickly and safely, without having to contend with other powers.

4. Marco Polo's Influence: The travels of Marco Polo had popularized the idea of the riches of Asia, which further fueled Columbus's ambition to reach the Indies. He thought that by finding a western sea route, he would be able to access these riches more effectively.