John Gill Commentary 2 Samuel 5:2

"In times past, when Saul was king over us, it was thou that leddest out and broughtest in Israel: and Jehovah said to thee, Thou shalt be shepherd of my people Israel, and thou shalt be prince over Israel." — 2 Samuel 5:2 (ASV)

Also in time past, when Saul was king over us
Even over all the tribes of Israel:

you were he that led out and brought in Israel ;
that led out the armies of Israel against their enemies, fought their battles for them, obtained victories, and brought the troops under his command home in safety; and the remembrance of these valiant acts of his, which then endeared him to the people, was now another reason for their choosing him king: and another follows, the chiefest of them all:

and the Lord said to you ;
when anointed by Samuel; for though what follows is not recorded in so many words, yet the sense of it is expressed in the anointing him to be king, whose office, as such, lay in doing the following things:

you shall feed my people Israel ;
as a shepherd feeds his flock; hence kings were frequently called shepherds, and David particularly, in which he was an eminent type of Christ, see (Psalms 78:71Psalms 78:72) (Ezekiel 34:23Ezekiel 34:24) (Ezekiel 37:24) ;

and you shall be a captain over Israel ;
the Targum is, "and you shall be king over Israel;" which gives the true sense of the tribes, and which was the chief and prevailing reason with them to make him their king; and which they, at least many of them, would have done before, even immediately upon the death of Saul, but that they were persuaded by Abner to yield obedience to Ishbosheth he set up.