Serial fiction has always been a thing. Most novels 150 years ago were written for magazines. Only in the past century did the write a novel as a complete book really take off. Even then though, authors often wrote trilogies where you wrote a third at a time. (publishers like this because people hooked on the first book at the library or discount store would buy the second and third at full price when it came out). Now in the web world a lot of great authors have figured out that patron and doing a chapter a week (or some schedule) is the most profitable way to write.