"Hashem miSinai ba VeZarach miSeir lamo, hofia meHar Paran…"
"Hashem Came from Mt. Sinai - Having Shone Forth from Mt. Seir, and Appeared at Mt. Paran" (Devarim 33:2)
Lest the nations of the World complain that Hashem was unfair in not offering the Torah to the rest of the world, Hashem did in fact offer it to all the other nations of the world, and was turned down by all.
Hashem first offered it to the descendants of Esav, who lived in the area of Mt. Seir, in accordance with the inheritance that Hashem had given them. When he offered them the Torah, they asked, "What are its laws?" When Hashem told them that one of its laws was "You shall not murder," they said, "How can we accept the Torah? That law goes against our very nature, as Yitzchak said to our father, Esav, "And you will live by the Sword!" (Bereshit 27:40)
He next offered it to Amon and Moav, who likewise turned it down. They asked, "What are the laws of the Torah?" When they heard that immorality was one of its main prohibitions, they said, "Our national origins are bound up with a story of immorality between Lot's daughters and their sleeping father. (Bereshit 19:30-38) Immorality has become part and parcel of our national character.
When he offered it to the descendants of Yishmael, they could not then, and they cannot now, deal with the prohibition against stealing (Vayikra 19:11), as the Angel of the L-rd said to our mother Hagar about our ancestor, Yishmael, "He will be a person without self-control, with his hand in everyone else's property, and everyone else's hand in his property, and he will camp on the borders of everyone else's land." (Bereshit 15:12)
It was only when He offered the Torah to the Jewish People that He found a Nation with the potential to live according to all the laws of the Torah. And they realized this potential by saying to Hashem, "Naaseh V'nishma, "We will first obey, and then understand," (Shemot 23:7), when He offered them His holy Torah.