I’ve wondered this before. I don’t know. A possibility is that, because the stars move and the constellations change over the course of the passing ages, many of the references are describing changes observed in the celestial bodies or, possibly, celestial bodies which were not listed by Ptolemy but which existed in ancient times none-the-less. I believe that anybody who claims to have perfect understanding of revelations is a liar. I make no such claims. I only point out that there are many references to astrological entities in the bible and it seems very probable that someone attempting to tell a story that spans ages would use the movements of the constellations and their resident stars as references to establish their timeline.
it also seems likely that ancient men spent a great deal of time and energy oberving and contemplating the stars while never really understanding them. I would bet that changes in the heavens 20,000 years ago did not go unnoticed. A supernova, for example, would have been big news even then; although it would be misunderstood and, consequently, would be described in a manner that was not altogether understandable by modern men.