How did Ögödei rely on Yelü Chucai during his rule as great khan?

During his rule as great khan, Ögödei relied on Yelü Chucai for his expertise in establishing a formal bureaucracy and a rationalized taxation system for the Mongol-controlled regions of China. Yelü Chucai, a trusted advisor to both Genghis Khan and Ögödei, persuaded Ögödei to spare the inhabitants of northern China. This decision allowed the Mongols to utilize the wealth and skills of the Chinese population, providing access to Chinese weaponry that later facilitated the conquest of the Song dynasty.12

Yelü Chucai was instrumental in creating the Central Secretariat, which centralized civilian administration and brought a degree of continuity to governance. He also implemented a system of land and poll taxes, as well as sales taxes, and established monopolies on certain goods, which significantly increased the Mongol court's wealth.3