Because going to the West would cost a lot of money, the government felt that it was a loss, so it began to close the sea, especially in the Qing Dynasty, which was extremely closed to the outside world. And won the respect of the western countries, want to see China himself. . . . . . . . . .

The standard answer is probably this idea. . .

Unofficial history said that he couldn't find Zhu Yunwen when he went to the Western Ocean, so he thought he didn't escape there, so he just looked for it in China. . . .

In the novel, Zheng He, a woman, thought that she might be forced into the palace by the emperor, so she flew with other men, called a real eunuch to play her, and let the imperial forces lobby the emperor not to go to the West again. . . . .

Well, I think the reason is huge expenditure, low income, fiscal deficit and so on. . . As for vision, people's thinking is limited there. At that time, it could really solve some political problems in a short time.