Im glad you brought this story up. It does not seem that the people Moses was leading thought too much of Moses's God.
It is estimated that there were more than a million persons who were lead out of Egypt. And that was a mixed multitude---Egyptians and possibly others who choose to believe GOD after the plagues.
Moses leaves for a few days and right away Aaron, the brother of Moses, gets the poeple to give him their jewlery and Gold and makes a Golden Calf (Symbolic of El and/or his consort Asherah).
There was no time frame in which MOSES was to return. The Creator GOD was instructing Moses in the ways which mankind was to live in relationship to GOD and one's fellow being. and Moses was recording the same. From day one of those forty, the people was afraid of death in the presence of the Almighty GOD. This was seen in the telling Moses for him to meet with GOD and you tell us--"All the lord says, we will do."
Thirty-nine days later some of the doubter's faith wavered and failed.
Not even Moses's own brother thought much of Moses' God apparently.
God didn't think much of those "stiff-necked people".
The "apparently" isn't a valid answer---only your opinion. Aaron did submit to those rebellion persons wishes.
Considering these people supposedly saw Moses's God part the red sea and so forth .. you would think that at least his own brother would believe in this God and so would the rest of the people.
By the same reasoning, Adam was presented with a mate---from himself---and failed to believe GOD.
It hasn't changed in 6000 years. It is your opinion which counts----NOT what GOD said nor did. That is still the lie which has been from the first doubt which entered into a created beings mind.
Moses comes down from the mountain and is not happy. Turns the Calf into powder and makes the children drink it.
Moses then bids the people choose sides (with "the Lord" or against). 3000 people chose against so Moses has them killed.
Now if 3000 poeple who actually saw the miracles of Yahweh first hand did not believe .. it is highly unlikely that these things really happened and that it was the hand of the editor's who wrote the story down some 1000 years later that were "adding lib" so to speak.
Since over a 1,000,000 persons were at the foot of Sinai, 3000 people is a few, but a dangerous group/mob.
How the story likely went is that Moses left out of Egypt after the Egyptians rebelled against Akhenaten (founder of monotheism).
Moses .. being close to the royal family as we are told, was probably a leader of that cult.
When the people rebelled against Akhenaten many folks adhering to the cult of Monotheism had to get out quick.
Moses was likely their "military" and spiritual leader. When the people rebelled against him he did what a good military leader does and crushed the rebellion within the ranks quickly and brutally .. killing 3000.
All with understanding, can easily see the results of a rebellious mind---then(Garden and Sinai) and today.