I have been observing a Facebook wide trend where post reach is decreasing while engagement is increasing. This trend was once interesting but has recently become startling. You see, posts are only being seen by those who are most likely to interact with them. Eventually, Facebook will only show your content to people who are fairly sure to like, share or comment on it. The problem is these users represent a very small part of your audience.
The Back Story
Up until about a year ago, when a Facebook page made a post, a substantial portion of their audience saw it.