what is meant by "the major burden in daniel is the tension between the kingdom of god and the kingdoms of the world?

"Daniel Isaacson frames his narrative with The Book of Daniel: the first epigraph and the final words of the novel quote passages from the Old Testament. The biblical character he identifies with was an interpreter of dreams for a cruel king who tended to forget his dreams. Daniel therefore needed to recreate the dream before interpreting it. Should he fail, he risked death, for the king threatened to cut him and his friends in pieces2. Referring thus to this specific biblical passage stresses interpretation as a matter of life or death and, in Doctorow’s novel, Daniel, the ever-dissatisfied interpreter, lives, whereas his past-oriented and catatonic sister Susan dies."