Why was Johann Sebastian Bach able to compose church cantatas at such a rapid pace in Leipzig?

Johann Sebastian Bach was able to compose church cantatas at a rapid pace—sometimes at a rate of one per week during his early years in Leipzig—because he and his contemporaries operated within a system that did not rely on the unpredictable arrival of "inspiration."

Instead, Bach utilized established musical conventions, techniques, and the generally rationalistic outlook of the Baroque era. By willingly embracing these traditional forms and regimens, he was able to invent or discover his musical ideas quickly. This approach allowed him to meet the heavy demands of his position as director of church music, where he was responsible for supplying music for multiple churches throughout the ecclesiastical year.1