The entire Jewish people personally experienced that revelation, each individual in effect becoming a prophet, and each one verifying the experience of the other. With their own eyes they saw, and with their own ears they heard, as the Divine voice spoke to them, and also they heard G-d saying, "Moses, Moses, go tell them the following ..."7 They did not receive the occurrence of that event and accept it as some claim or tradition of an individual, but they experienced it themselves. That public revelation, therefore, authenticated the bona fide status of Moses as a prophet of G-d, and the Divine origin of the instructions he recorded in the Torah. That, and that alone, is the criterion for the belief in, and acceptance of, Moses and his teachings, as G-d said to him, "I will come unto you in a thick cloud that the people may hear when I speak with you and will also believe in you forever" (Exodus 19:9).8
7 See Rambam, Laws of the Foundations of the Torah 8:1.
8 Ibid., ch. 8. See also Rabbi Sa'adia Gaon, Emunot VeDe'ot, Introduction: ch. 6 (and see there also treatise III: ch. 6); Rabbi Judah Halevi, Kuzary I:87; Sefer HaHinuh, Introduction (the Divine Code by Rabbi Moshe Weiner, Ask Noah International, 2018, p 35).