Traditionally many authors were paid by words/pages. I’d imagine revenue has a lot more to do with the number of books sold nowadays. This isn’t new specifically to the time range studied in this article, but many of the classic novels that come to mind were definitely influenced by an incentive (other than content) for a higher word count.
Tolstoy, for example, took advantage of being paid by the amount of content by basically saying everything twice in a different way. This style makes for relaxed reading, because you’ll catch the content the second time if not the first, but it’s obviously not necessary. Dickens, as another example, also published less-dense material on a regular basis based on his contractual obligations (his novels actually read better if you follow the original publication schedule). His books were just part of another publication, basically a newspaper. As long as he delivered a satisfactory amount of core-story each week, he kept his job. This incentivized him to split up the best parts and add some fluff.
I’m no less satisfied by a good modern book than War and Peace. I enjoy both for different reasons.