The Isrealites stopped halfway in their conquest because they got comfortable, lethargic and complacent. They traded God's best and was trapped in a cycle of "covenantal amnesia," failing to fully occupy the land and turning to false gods. Through Othniel whose name means "Lion of God," we see how God isn't bound by our social background or family history to bring about deliverance. Isreal found a surprising ray of hope in the first judge , Othniel who was technically an outsider. God's grace is always greater than his judgement.
The book of Judges reveals a nation in desperate need of a redeemer. They
needed more than military relief. The lawlessness and waywardness of the period
proved that human effort is not enough.
Not all judges were good. Some were flawed (some more than others). Each
judge, however, serves as a prefiguration of the ultimate judge, the messiah, Jesus
Christ.