That is only a couple thousand years before Socrates and Aristotle were creating Western Civilization in Greece with an Indo-European language.
Also, agriculture began in that general area about 10,000 years ago. Hard to believe that resident farmers did not instantly see that horses could pull a plow.
I think the issue was developing a bit to control/domesticate the horses, which some archaeologists found evidence of about 4800 BC in the Russian steppes. The Yamnaya culture, referenced in the article, spread from present day Georgia/Azerbaijan, reaching the Danube Valley and the Carpathian Mountains in about 3100 BC. My source: an excellent book called “The Horse, the Wheel and Language” by David W. Anthony.
Why would they want a horse to pull a plow? Oxen do a much better job, are less prone to injury and other illness and provide more and better meat.
Horses are good for exactly one thing to get you from one place to another quickly. They also ride the equine short bus as far as brains go. That is why they are ridden in to battle. You try to ride a donkey toward a line of people with spears and donkey will "NOPE" right off the field. His mamma didn't raise the dumb ones.