When the people saw that Moses delayed to come down from the mountain, the people gathered themselves together to Aaron and said to him, "Up, make us gods who shall go before us. As for this Moses, the man who brought us up out of the land of Egypt, we do not know what has become of him."
Despite their recent miraculous experiences, and despite the commandments which they heard from God, the people grow impatient and move quickly into sin.
They pressure Aaron into making a false god for them to worship; a golden calf which is clearly just a made-up god.
This shows that miracles and knowledge do not automatically translate into proper understanding and faith. If the people had a proper understanding they would have patiently waited, trusting that the God who had delivered them out of Egypt could also keep them safe and deliver them into the land which was promised to them.