Chapters 7 and 8 are not in chronological order. They happened while Belshazzar was still the king, before the rule of Darius and Cyrus that was discussed in chapter 6.
In Daniel's vision, he saw animals that were symbols of other things. Later in the vision someone explains the meaning of those symbols. (See: [[rc://en/ta/man/translate/writing-symlanguage]])
This is background information to remind the reader that this is Daniel's second vision. AT: "had a second vision appear to me" (See: [[rc://en/ta/man/translate/writing-background]])