Not sure if this is true, he got "lucky" with technological advantage of warfare (Mongol bows) compared to other nations close to him as horse archers were literally "meta" to fight vs heavy/peasant infantry same case as Crassus fighting Parthians.
His great accomplishment was marrying that with the ability to besiege walled cities. Nobody expected barbarian horse archers to be able to do that.
Even if we would accept that their bows were better then some other steppe peoples, he still thought many people that for sure had the same bows as he did.
In fact, most of his life, he thought people who had the same technology, including the invasion of the Qara Khitai.
Then the Jin had allies that likely had the same bow technology. However it seems most of those allies just switched sides.
Only the Khwarazmian Empire and Xia likely didn't have significant troops armed the same way.