Adam Clarke on Daniel 3:30

Then the king promoted, etc. - He restored them to the offices which they held before the charge of disobedience and treason was brought against them.

At the end of this verse the Septuagint add, "And he advanced them to be governors over all the Jews that were in his kingdom." This may be the meaning of the latter verse. They were more likely to be set over the Jews than over the Chaldeans.