Happy Birthday Aharon HaKohen

Not long ago, Jews would chant “Halleluya” 123 times during Hallel.
Chazal say this corresponds to the 123 years of Aharon’s life.
The Rambam brings this l’halacha.

Why is Aharon given this Hallel distinction more than any other tzaddik?

Shabbos Shalom!