In chapter 9 we see the use of these genealogies, for the names given (down to verse 34) are of those who had returned from the seventy years captivity. (See Nehemiah 11; and chapter 7, verses 5 and 64, 65).
Each of the Levites had his service to perform, of that little flock of chastened souls who returned with Ezra and with Nehemiah to the glory-departed city of Jerusalem. The "transgression" of the people (verse 1) had brought this ruin and shame upon Israel, and their return was not in independence, but as subjects of the great Cyrus (Ezra 1).
Some of Ephraim and Manasseh were among the returned exiles (verse 3 of our chapter), as well as those of Judah and Benjamin. Had the first named joined the later when Cyrus opened the way; or were they living in Judah's land when the captivity took place? We can only conjecture as to this.
Verse 35 begins the detailed history, giving the genealogy of the king the people had desired, Saul the son of Kish of Gibeon; but not only to Saul and his four sons, but on down the line through Mephibosheth (Merib-baal) to the period in which this book was written. This is grace indeed. Saul had brought judgment on himself and his house, but God remembers mercy. To Him be eternal praise!