Astrological ideology is based on the unifying theme that the movement of time has a ‘natural’ correlation with human endeavor. Myths of how time functions for humanity revolve around this idea, that movement of the heavens, time’s progress, and people are all interconnected. Astronomers learned to link the movements of the heavens with the ‘natural order’ on earth, and civilizations eventually began to perceive this connection as a fact, leading to the concept of ‘as above, so below.’
Now, there’s nothing wrong with this idea. It’s a lovely thought, that we are all connected, that nature and humans are one. Time as a motif implies movement, and movement implies progress, but for many, the idea of progress is a sociopolitical myth. Humans also tend to believe either in a linear version of time, or a more circular version, as in, we all come back around again (via the laws of karma, reincarnation, etc.) as well as an interwoven version, where we are all moving toward either a better, more Utopian version of the future, or toward a more dystopian version, where what awaits us are the flames of the coming Apocalypse. Astrology is seen as a way of measuring this movement of time as we spend it on Earth, bound as we are by the limits of time.
So, we tend to use time as a myth and a metaphor, and astrology fits very neatly into that schema. If you are at all interested in this subject, I recommend Nicholas Campion’s The Great Year: Astrology, Millenarianism, and History in the Western Tradition, in which he discusses the political implications of astrology as a myth and an ideology.