Why was the superiority of the Chinese over the Europeans in overseas voyages in the 1420s

Why was the superiority of the Chinese over the Europeans in overseas voyages in the 1420s by the middle of the 15th century replaced by their lag?

After overthrowing the Mongol yoke in the 1360s, the Chinese experienced a cultural boom and began their maritime expansion. Their ships reached India and Madagascar before the Portuguese reached the Cape Verde Islands. But the rapid growth of bureaucracy in the Ming empire soon made overseas voyages unprofitable, and they ceased. It was the same with typography. The Chinese were the first in the 11th century to create movable type from baked clay, but did not invent metal type, since the demand for new books was low.