Anyone know why the Protestant Bible deleted this?
Because "the additions to Daniel," three chapters, were not found in the Hebrew or Aramaic text, and were not part of the Jewish Tanakh.
"The additions to Daniel" are contained within "Protestant" Bibles as part of the Apocrypha or Deuterocanonical books, which are bound separately in the back. They're regarded as edifying but not divinely inspired.
Some more recent "Protestant" Bibles do not contain the Apocrypha, however no one "deleted" anything.
"Bel and the Dragon" is regarded as Apocryphal by "Protestants" too, would you like to discuss that one?
Luther decided that only the Hebrew or Aramaic portions of the Old Testament should count (part of Daniel and a bit of Ezra are in Aramaic). Perhaps the reason for this was that he wanted to get rid of a verse in one of the books of Maccabees which was used by the Catholic Church to support the doctrine of purgatory and praying for the dead. The books of Maccabees are preserved only in Greek.