Why did Yoga Sutra become a book in the 5th century?

The oldest and most authoritative book about yoga is called Yoga Sutra, written by a man named Bo Dian Li. It is generally believed that Yoga Sutra was written in the 5th century. But this does not mean that yoga began at that time, and the history of yoga is much earlier. In ancient times, India had no writing tools, and all the classics were passed down orally. In order to be easy to remember and recite, sentences are short and often rhythmic, which is also the reason why ancient Indian poetry is developed. By the 5th century, oral things could be written into words, and Berry became one of the heroes who summed up thousands of years' legacy.