Literally, the sentence reads, And the people did this thing.
The point is that nobles and officials restored lands and houses (and children) to their rightful owners and also supplied the needed money, grain, wine and oil, as they had promised. But restoring and supplying requires persons who will physically receive what’s given. Hence the phrase the people
refers to both parties, the oppressors and the oppressed. They are drawing closer to each other and reconciling with one another.
13 I also shook out the fold of my garment and said, “So may God shake out every man from his house and from his labor who does not keep this promise. So may he be shaken out and emptied.” And all the assembly said “Amen” and praised the LORD. And the people did as they had promised.