The Hebrew may be subject to two different interpretations.  Aaron said, “These are your gods, Israel, who brought you out of Egypt.” (Exodus 32:4)  Later, Jereboam set up two calves–one in Dan and the other in Bethel–and said that they were Israel’s gods.  The intent of both Jereboam and Aaron, it seems, was to give Israel a visible “god” as a symbol and representative of YHWH. In fact, in Exodus 32:5, Aaron told the people that they would use the calves to have a celebration of YHWH. All the other nations had visible, physical representative of their gods, so Israel needed them as well.  This was their “logic.”  So, they probably would have defended their actions as promoting the worship of YHWH, not idolatry.  However, two things about that:  1. God clearly considered this idolatry, even if, supposedly, the calf (or calves) were supposed to be idols of YHWH.   and    2. It was clear and utter foolishness if either Aaron or Jereboam thought this would not lead to blatant idolatry–seeing YHWH as merely a national god amongst many nearly equal other national gods, of which YHWH was the most powerful, but not all-powerful.

So, I would say that the answer is both (but more that it was to worship YHWH than it was to worship other gods)!  Either way, it was a terrible mistake.

John Oakes