To learn more about the world and show other countries his power.
题意:
为什么朱棣要让郑和航行到许多不同的国家?
细节理解题。根据第二段,第一句The King wanted to learn more about the world and show other countries his power.皇帝想更多地了解世界,向其他国家展示他的力量。可知,朱棣要让郑和航行到许多不同的国家的原因是想更多地了解世界,向其他国家展示他的力量。故答To learn more about the world and show other countries his power.