Walton didn’t discover the concept ~ buy low, sell high ~ is ancient wisdom.
I know you like many here dislike Walmart for reasons I can’t understand, but you miss the point. He completely disrupted American business and revolutionized the relations between those who make things and those who sell things. Walmart is a truly great success story.
He did not just buy low, he created low. His successors followed the path and improved it to the point there are no equals.