I know that in China they had invented a repeating crossbow and a crossbow that shoots 2-3 bolts per shot. Why was this not utilized in the rest of the world?
While I am no expert in this subject I do own a text book on ancient China!
So from a quick read I found that the first crossbows were deployed in around the third century BCE, these were "mobile" though they were around 600 lbs. (270 kg) and could shoot up to 1000 yards (900 m). These types of crossbows were similar to the Roman Ballista in size. It was not until much later that the repeating crossbow design came, in the eleventh or twelfth century CE. This repeater crossbow was capable of firing several bolts in order.
Most historians (please don't hurt me) would classify the end of "ancient history" at around the 7th century CE. So it might not be and "ancient" invention. Though my information is coming from a book written 10 years ago.
Source: China: Empire and Civilization