The Giving of the Torah is a singular event primarily because of the event’s influence on the Jewish Peoples essential nature.
Due to the content and character of the Giving of the Torah, it alone formed the singularity of the Jewish People for all time.
Clearly, there is an element of distinctiveness in the very fact that the Jewish People at its inception left the house of bondage.
But this distinctiveness could not have taken on its full significance without the acceptance of the Torah, which inscribed the exodus from Egypt as an enduring memory within the collective Jewish memory.
–Rabbi Adin Steinsaltz