The Scriptural texts have over time been subjected to many deliberate amendments, including efforts to make them align with contemporary thinking. (No different from the intentions of the Watchtower Society.)
Thus when the dominant writers were at least monolatrists (recognizing that there were gods apart from Yahweh -- "you must not have other Gods before me") the original passage was acceptable.
I need to add that Deuteronomy as we have it comes from the 6th century BCE, when Monotheism was trying to become the dominant force. Contemporary familiarity would have limited the extent of change the Deuteronomists could invoke at the time.
However, Monotheism had succeeded, by the time the Scriptures were translation into Greek, so the text was amended.
The Book of Jubilees was written about that time (possibly by the Sadducees) and the following from "Crucible of Faith" pages 159-160 shows how they amended the text to suit their teachings.
On earth, angels served as the leaders or rulers of
particular nations or territories, and in this capacity they closely resembled
the pagan gods of old. In fact, one passage in Deuteronomy shows a direct
continuity in those ideas. In the original text, God assigned nations according
to the number of “the sons of God,” presumably an acknowledgment of the reality
of rival deities. That nod to polytheism embarrassed later readers, and in the
Septuagint translation God sets nations and boundaries “according to the number
of the angels of God.” Once upon a time there were gods, who were transformed
into tutelary angels or spirits, who in turn became thoroughly godlike. This
idea of national guardians is well developed in Daniel (10:13, 10:21, 12:1). …
Given its pervasive hostility toward Gentiles, it is [the
Book of] Jubilees that presents these
figures in the most sinister and exclusive terms. Yes, says the author, “there
are many nations and many peoples, and all are His, and over all hath He placed
spirits in authority to lead them astray from Him. But over Israel He did not
appoint any angel or spirit, for He alone is their ruler, and He will preserve
them and require them at the hand of His angels and His spirits.
That ran against the common assumption that Israel did
indeed have a tutelary figure, namely, Michael. But whatever the exact identity
of such figures, the idea of territorial spirits lent itself to visions of
earthly conflicts being mirrored in the heavens, to clashes of angelic and
He sanctified it, and gathered it from amongst all the children of men; for
there are many nations and many peoples, and all are His, and over all hath He
placed spirits in authority to lead them astray from Him. But over Israel He
did not appoint any angel or spirit, for He alone is their ruler, and He will
preserve them and require them at the hand of His angels and His spirits, and
at the hand of all His powers in order that He may preserve them and bless
them, and that they may be His and He may be theirs from henceforth for ever.
at: http://www.pseudepigrapha.com/jubilees/15.htm ]
[Doug's note: Daniel as we have it was written in the 2nd century BCE. The RC version is a bit different.]