R’ Moshe Alshich zt”l (Alshich Al HaTorah) would say: “'ויכתב משה את השירה הזאת ביום ההוא' - Chazal say that in one day Moshe wrote the entire Torah. Why? Because Moshe knew that the people might say, ‘We have the Aseres Hadibros, why do we need the whole Torah?’ Thus, Moshe needed to perform this miracle to show that the Torah was not written by him, but by Hashem himself. Since it is not possible for me to write the whole Torah in one day, it must be Hashem Himself wrote the whole Torah and not only the Aseres Hadibros.”
A Wise Artist would say: “Being brilliant is no great feat if you respect nothing.”