Ironically Genghis Khan really is one of history's few exceptions here. He had umpty-dozen precursors, all of whom are obscure even to most history-inclined people. But then this one dude who was eating rodents to survive hits it big and he literally rewrites the world.
Flip side of that is that he very much had umpty-dozen predecessors, many of whom were every bit as genocidal as he was, and almost all of them with similar relative advantages to populations around him and they're the most niche historical interest among historical interests.
I would love to see a book of history context. For example - the Italian renaissance...they suddenly got very smart in Italy? Got rid of Roman lead pipes? Or Genghis scared the centers of culture starting in China all the way to Baghdad...the refugees' kids ended up 2-culture kids in Italy.