This is the makings of a Conan the Barbarian film. We’ll never know the exact history
Horsebased societies had to constantly be on the move to find good pasture for their horses. Cattlebased societies don’t have to move because cattle can suck any nutrient out of just about any fodder or silage as cattle have to gut to do that. Coupled with metallurgy, it was a weapon of mass destruction. End of story.