I doubt that we should be looking for literal history in any of these ancient records. They are religious histories, written for propaganda purposes at the time of its composition. In other words, study is required into the history of the writing of the history (historiography).
I have no doubt that Daniel was written in the 2nd century as a means of providing comfort and messages to the persecuted without their overlords being aware of the intent. In other words, the overlords were looking at the stories literally rather than as literature. We should not fall into the same trap.
It helps, as with any other part of Hebrew and NT writings, to search for the chiasms. These are important; they had helped the illiterate to remember stories and it facilitated the stories being told, orally. At any time until quite recently, less than 10% of a population could read and probably less than 2% could write (a very different discipline). So the poetic structure of chiasms was important to the Hebrews (and the NT) and it might be that when you work out the chiasms, that might clarify apparently strange transitions. (I am aware of: "The Literary Structure of the Old Testament" by Dorsey.)
Other issues with Daniel include the difference between the LXX and MT (see, for example, mention in "Aramaic Daniel and Greek Daniel: A Literary Comparison", by Meadowcroft) and recognising the issues raised in "The Cultic Motif in the Bok of Daniel", by Vogel.
I am sure I do not need to labour the point that we have to read any ancient (such as Late Iron Age) writing through the lives of the community as it was when a piece was written, not through our ways of thinking.
Dou