Short-form and long-form are essentially different media. (I'd add that serialized long form, aka prestige TV, seems to be doing pretty well right now at least at the top of the pile.)

Short-form media has always been harder to monetize. We've had the technology for a long time to sell individual short stories, articles, etc. It doesn't seem to work very well. (Tangent. Why can't I buy an arbitrary short story on Kindle?) Most authors of 300 page books don't make much money either but there does seem to still be a fairly robust writing and publishing pipeline there.