ירמיהו י:כא פירוש: רש״י

For the shepherds The kings.

they have not prospered They have not prospered in their kingdom. Comp. (Prov. 17:8) “To all that he turns, he will prosper (ישכיל).

their flocks Heb. מרעיתם, lit. their pasture, the flocks of their pasture.