Also, like, it wasn’t just a “decision to stop” it was the end of a coincidence of factors. The mid century climatic conditions that led to several years of poor grass growth, with the combined hunting efforts of European American settlers on rail roads supported by the army’s policies against the Great Plains Indians, south eastern Indians displaced in to the great planes, and Great Plains Indians intensifying hunting via sophisticated methods they’d developed using horseback and fire arms, all driven by a demand for buffalo hides for use in industrial machinery. The end of the bad climatic conditions and the collapse of the hide trade due to development of other industrial materials is what stoped the over hunting.

With the pressures of hunting decreased and a historic climatic event over, the population was able to rebound somewhat, but, due to the encroachment of farms and ranching never really recover. Also the genetic bottleneck of the population probably hasn’t helped things but that’s not super well studied.