Also consider that while star sign might be the stated reason for incompatibility, the truth could have been an impression or gut feeling and so the astrologica

Also consider that while star sign might be the stated reason for incompatibility, the truth could have been an impression or gut feeling and so the astrological mismatch is simply a way to give a reason for their feelings, whether done consciously to save face, or subconsciously to have something decisive to latch onto.