Everyone did as they saw fit.

Judges 21:15-25
So that is what the Benjamites did. While the young women were dancing,each man caught one and carried her off to be his wife. Then they returned to their inheritance and rebuilt the towns and settled in them.
In those days Israel had no king; everyone did as they saw fit.
Why?
The writer has no need to point a moral. The simple statement of verse 25 is sufficient. The whole book makes plain the disastrous(慘重) consequences of breakdown of authority, when people become a law unto themselves, setting their own standards of perissiveness.
How?
There is disastrous consequences of breakdown of authority of the Lord. To be a good servant of the Lord.