And YHVH said to Moses, "Behold, I am coming to you in a thick cloud, that the people may hear when I speak with you, and may also believe you forever."…
#exodus 19:9 #yitro

Dramatic miracles are rarely just for the benefit of the one receiving them, but for those who are watching. God didn't need to come to Moses in a thunderous cloud on a mountain top. He could have whispered to him in his tent. God wanted the people to know that every word Moses spoke to them in the wilderness was from God, not from his own imagination. They were unable to hear God with their own hearts, so God set Moses as an intermediary, but what good is an intermediary if the people won't listen to him either?