That's one of the biggest things that I find amazing, that they would be able to see the hand of God in action. To see the the pillar of fire at night and the cloud by day, and to see the parting of the sea, the destruction of the Pharaoh and his army, but then shortly afterwards they are making a golden calf to worship!God did this as a pillar of fire leading a nation in the wilderness, didn't He? That sort of "seeing is believing" lasted less than 40 days before they built themselves an idol to worship, right?
Guess God can't go on a mountain retreat if seeing is believing.