Why did the Chinese stop the voyages of Zheng He?
There was a power shift in the Forbidden City as well as a Emperor change. Political interest focused to internal matters rather than Foreign interests.
Zheng He was a eunuch. In the Court of the Yongle Emperor (1400 to 1424) a group of Eunuchs held power under the Emperor. Their influence created the push to Naval exploration and interest in trading and foreign lands.
The Scholar-Bureaucrats began it hold more influence in court. These men raised in the the Confucian tradition had the many internal interests of China as their focus. The Naval voyages were expensive for there benefit and only one voyage happened after the power shift.