No explanation is necessary. It happens.
WESTERN astrology is NOT based off the actual constellations, so the precession of the equinoxes does not impact Western astrology.
And Sidereal/Hindu/Vedic astrology USES the precession. Not exactly but so (in that the sizes of the zodiac constellations vary hugely ... but in Vedic astrology EACH Sign is alloted only/all-of 30 degrees regardless of the size of the constellation).
Western astrology is based off the seasons. Wherever the Sun appears to be, at the moment of the Spring Equinox, that location is labelled "0:00:00 (degrees:minutes:seconds) of Aries". And the first 30 degrees around the ecliptic, from that point is called the SIGN (NOT the "constellation") of Aries. The second set of 30 degrees around the ecliptic is labelled "Taurus".
Your question shows that you understand astronomy.
But not astrology. Most of the general public misunderstands astrology.
And that is fine. You don't have to understand astrology.
But you would appear better-informed if you understood astrology before you tried to tear it apart.
Professionally-certified astrologer, also with a B.Sc.