Daniel 2: A dream shows that Nebuchadnezzar's kingdom (head of gold) will be replaced with subsequent kingdoms.
Daniel 3: A huge image entirely of gold (Babylon will never be replaced).
Daniel 4 (v 30 especially): Nebuchadnezzar boasts that Babylon's glory is solely due to him. Story ends with Nebuchadnezzar acknowledging the supreme role of the Hebrews' God.
There is thus a continuing theme, a composite objective of these stories. They employ mythical elements (a fire that burns selectively?) and other elements that better fit a superstitious culture.
To whom were this set of stories addressed? What message of comfort or divine purpose did they contain? The messages had to have meaning for the community they were being addressed to, where the circumstance confronting Daniel and his cohorts was being repeated. Such considerations are among several that point to these stories being collected, assembled, and promoted during the persecution of the 2nd century BCE.
These stories had meaning to the intended audience without raising the suspicions of their terrifying persecutors. Understanding the 2nd century context of the book of Daniel provides meaning to its contents.
Doug