The time of Mongolia's Western Expedition was13rd century, while the knight system in Europe was actually established in14th century, and the plate armor used by knights only appeared in15th century, that is to say, there was no such thing as heavy cavalry in Europe at the time of Mongolia's Western Expedition.

/kloc-in the third century, the level of science and technology in the east was much better than that in the west, and the equipment of the Mongolian army was much better than that of the European army, which was basically the same as that of the United States and Iraq now. European cavalry actually wore chain mail and leather armor, so they couldn't guard against bows and arrows. Mongols, on the other hand, equipped a large number of scales and half boards with oriental technology and productivity, which provided good protection for the long swords and short bows equipped by Europeans.

It's just that/kloc-European knights after the 0/5th century left a deep impression on everyone, so when I talk about Europeans, I think of knights in plate armor. Finally, the war between Mongolia and Europe became the battle between Guan Gong and Qin Qiong in everyone's mind,15th century European knight and12nd century poor Mongolian cavalry who didn't even wear leather armor.