The judges come to Nephi to ask that he pray to have the famine end. It is important to note that verse 10 declares that they “have swept away the band of Gadianton.” At least symbolically, Mormon is telling his readers that it will be possible for the nation to repent because the destructive Gadiantons have been removed.
The Gadiantons appear and disappear throughout Mormon’s story, starting in the beginning of the book of Helaman. The first time they disappear, they come back, having learned their secret combinations from the devil himself. This time, however, they disappear, and bury their secrets in the earth. Mormon is never dealing with a perpetuation of the exact same band, but is dealing with the designs of the band of robbers and their secret combinations.
Nephi prays for restitution of the rains because the destroying Gadiantons have now been destroyed (verse 11).