Why did such Chinese inventions as the compass, gunpowder, paper, porcelain, and crossbow penetrate Europe

Why did such Chinese inventions as the compass, gunpowder, paper, porcelain, and crossbow penetrate Europe with a “delay” of several centuries?

Each of these inventions is the fruit of high technology, and the technology is poorly transmitted through the contact of two peoples with very different levels of social development. A multi-layered “barbarian gasket” between China and the Mediterranean hampered such transmission.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.