In ancient times, astronomers and astrologers used the positions of celestial objects to mark important dates and events. They noted that the vernal equinox occurred when the sun was in the background of the Aries constellation. This observation led them to associate the start of the zodiac with Aries.
Over time, this convention became established and Aries remained as the first sign of the zodiac. This placement has no direct correlation with any personality traits or characteristics associated with people born under the Aries sign. It is purely a matter of astronomical observation and historical convention.