1)
What did the commoners do?
1.
Radak: One who is stronger than his colleague, he oppresses and steals from him, for there is no law [enforcement] in the city.
2.
Malbim: They correspond to lead, which is the most inferior. They oppressed, stole and afflicted the poor.
2)
Why does it say "b'Lo Mishpat"?
1.
Radak: Refer to 22:29:1:1.
2.
Malbim: There was no Mishpat in the land; everyone did what was straight in his eyes.