That’s also a great explanation Dave Tesla. But the innermost (Chassidic translation of the “real” reason) is that weeks earlier at the giving of the Torah, the Jews saw a figure of the face of an ox on the angels carrying G-ds throne. They thought—good enough for G-d....good enough for us! And no human frailties! (they were disappointed that Moses chose (seemingly to them) to stay in heaven rather than come back and lead.
The Golden Calf
During the many years that the Israelites were in Egypt,
it is evident that they worshiped the Babylon idols.
Ezekiel 20
4 “Will you judge them? Will you judge them, son of man?then confront them with the detestable practices of their
ancestors
5 and say to them: ‘This is what the Sovereign Lord says: On the day I chose Israel, I swore with uplifted hand to
the descendants of Jacob and revealed myself to them in Egypt. With uplifted hand I said to them, “I am the Lord
your God.”
6 On that day I swore to them that I would bring them out of Egypt into a land I had searched out for them, a land flowing with milk and honey, the most beautiful of all lands.
7 And I said to them, “Each of you, get rid of the vile images you have set your eyes on, and do not defile
yourselves with the idols of Egypt. I am the Lord your God.”
8 “‘But they rebelled against me and would not listen to me; they did not get rid of the vile images they had set their eyes on, nor did they forsake the idols of Egypt".
It is no wonder that they returned to the idols the moment they thought Moses might not return to them. They insisted
that Aaron make them a golden calf.
Exodus 32
5. So when Aaron saw it, he built an altar before it. And Aaron made a proclamation and said, “Tomorrow is a feast to the LORD.”
6 Then they rose early on the next day, offered burnt offerings, and brought peace offerings; and the people sat down to eat and drink, and rose up to play.
Not only did they bring their sacrifices to the rising sun, but also the idol was golden, the color of the sun.
After the death of Solomon, king Jeroboam caused Israel sin by worshiping two golden calves he had made.
1 Kings 12
28. So on the advice of his counselors, the king had two gold calf-idols made and told the people, “It's too much trouble to go to Jerusalem to worship; from now on these will be your gods-they rescued you from your
captivity in Egypt!”
Stephen’s Address: The Call of Abraham
Israel Rebels Against God
The Golden Calf (aka Nimrod, Moloch, etc)
Acts 37
“This is that Moses who said to the children of Israel,
‘The LORD your God will raise up for you a Prophet like me
from your brethren. Him you shall hear.’
38
“This is he who was in the congregation in the wilderness
with the Angel who spoke to him on Mount Sinai, and with
our fathers, the one who received the living oracles to
give to us,
39
whom our fathers would not obey, but rejected. And in their
hearts they turned back to Egypt,
40
saying to Aaron, ‘Make us gods to go before us; as for this
Moses who brought us out of the land of Egypt, we do not
know what has become of him.’
41
And they made a calf in those days,offered sacrifices to the idol, and rejoiced in the works of their own hands.
42
Then God turned and gave them up to worship the host of
heaven, as it is written in the book of the Prophets:
‘Did you offer Me slaughtered animals and sacrifices during forty years in the wilderness,O house of Israel?
43
You also took up the tabernacle of Moloch, And the star of
your god Remphan,Images which you made to worship;
And I will carry you away beyond Babylon.’
http://www.jewishencyclopedia.com/articles/7907-host-of-heaven
The “host of heaven” is mentioned as the recipient of idolatrous veneration (Deut. iv. 19, xvii. 3; II Kings xvii. 16, xxi. 3, 5; xxiii. 4; Jer. viii. 2, xix. 13; Zeph. i. 5). The express mention of sun, moon, and stars as forming the “host of heaven” in this connection leaves no doubt that astral bodies and their cult are referred to. Sidereal worship was practised among the Canaanites, as many old names of cities (e.g., Jericho = “moon city”) indicate, and the astral character of the Assyro-Babylonian religion is well authenticated. The cult of the “host of heaven” was in favor among the Hebrews, but whether in imitation of the customs of their neighbors or as expressing their own original polytheistic religion (as suggested by Hommel) remains a matter for conjecture. Certain kings are mentioned as especially devoted to this form of idolatry (e.g., Manasseh and Ahaz; II Kings xxiii. 3, 5, 12). It is an open question whether (Jer. vii. 18, xliv. 17-19, 25) should be read “queen of heaven” or “kingdom of heaven.” If the latter reading be accepted, “host of heaven” is synonymous; and even if the pointing indicating “queen of heaven” is preferred, the phrase throws light on the connotations of the other phrase (Stade’s “Zeitschrift,” vi. 123 et seq., 289 et seq.; Schrader “Sitzungsberichte der Berliner Akademie,” 1886, pp. 477-491; “Zeit, für Assyr.” iii. 353-364, iv. 74-76).