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The agricultural revolution was perhaps the most important step in human development. There could never have been an industrial revolution without an argicultural revolution. The Mongol horde were hunter-gatherers. They may have been fierce fighters, but they had strict limitations due to the nature of their society. Eventually, the porridge-eaters can build guns and tanks, whilst the Mongols are still waving spears and riding horses.
Were they now. Fascinating! Can you spare more of your deep knowledge and understandings of reality?
Note to interested people: 'nomadic' is not equal to 'hunter-gatherer'. Neither term implies anything about diet either, although a common reason to be nomadic is that the livestock being raised need forage, and that is what the people of the steppe were up to.
'hunter-gatherer' economies are not conducive to the formation of organized societies of any scale, and certainly not once which can conquer a large percentage of the earth's surface and arrange taxation from it. One of the few genuine hunter-gather societies where an economy of any substance developed was on the NW coast of the North America (my stomping grounds), and this seems to have been associated with the phenomenon of salmon runs (which emulated seasonal harvests in agrarian societies to a degree.)