As an author from time to time, I am keenly sensitive to the dynamic where so many books could have been a single essay, but there's no money in essays.
Unless you have something to sell, and presto, so many essays and blog posts are really advertisements for the author or their employer.
Things like business books in particular may benefit from a somewhat longer-form article that fleshes out stories, case studies, and examples. But most of them don't need to be 250+ page books.
A novella? A short story? Both of these are common enough that I find this particular example rather strange.
ETA: And now I see it's in the context of non-fiction, ignore this. But I remember seeing novella-sized non-fiction books around about a decade ago, they were just not that common.
Years ago, Philip Greenspun wrote a post noting that there was no real middle ground between a magazine article and a book. (This was in the context of the web maybe addressing this--though it mostly hasn't, longreads and things like that aside).
Something either fits into low single-digit thousands words length or it needs to be a 250+ page book. In some ways, shorted attention spans make this sort of thing even worse. We still have books but, in my day job, we've mostly found that the 3,000 word white papers we used to crank out have largely been replaced by blogs and blog series.