Mongols are part of the Turkic group and look at their success using large scale invasion at rapid force. I’m not talking about the recent Mongol invasion but thousands of years ago where Nomadic Turkic empires like Huns, Scythians and the likes were around who bullied, intimidated and invaded neighboring Empires in Asia and Europe, and caused a huge migration shift that caused the split between Western and Eastern Roman empire.
Having a Nomadic lifestyle breeds toughness and produce warriors like the North Caucasus today.
There’s a reason why there’s multiple huge ancient walls, barriers and forts in China, Dagestan, Iran and the Darial Gorge between Russia and Georgia that protects Central Europe. They were being built to protect themselves from the barbarians (hence Turkic regions being surrounded by walls).
So, if they couldn’t be stopped in the past then it’s genetics and they’re predispositioned to be stronger than others.