"Eileh Elokecha Yisroel Asher He'lucha Mai'eretz Mitzraim"
Rashi (Exodus 32:1) says that when the Jews made the Egel, they actually wanted to make many gods - seemingly they strayed from monotheism completely and wanted to go back to polytheism.
The Ramban (ibid) argues with Rashi for a number of reasons that he brings out from the text and takes the approach that they really just wanted to replace Moshe because Moshe was gone - i.e., they needed new middle management: 1)The Jews weren't fools, how could they say this took them out of Egypt if they just made it? - They wanted someone like a Moshe who could do those things
2)G-d, when he told Moshe to destroy the people, it wasn't for initially making the calf, it was for serving the calf - because the calf itself wasn't necessarily bad
3)If they really made it to serve as a G-d - how would they allow Moshe to destroy it - they should have killed him for the sake of their new god? ואלו היה להם לאלהים, אין דרך שיניח אדם מלכו ואלהיו לשרפת אש, הן ישרוף את תועבתם לעיניהם ולא יסקלוהו:
For these reasons and more - he argues with Rashi But, doesn't he say that in the end, the Sin of the Egel was that although they had good intentions initially, they did deify it and sacrifice to it - so why isn't question 3 a question on the Ramban as well - why didn't they kill Moshe if this was their new god?