Israel had leaders, but no leadership. Rather than pray for direction (Judg 1:1) or God to provide an Ehud, the men of Gilead went to procure a deliverer of their own.
Someone remembered Jephthah. Their choice wasn’t without God’s approval. The sovereign God has left nothing to chance. The One who knows when even a single bird falls dead is surely aware when his people suffer (Mt 10:29-31). In His sovereignty, God led them to Jephthah, a man of their own choosing just like King Saul (1 Sam 8:18-22). Sometimes God demonstrates His sovereignty by giving men what they think they need or want.
God empowered Jephthah to deliver His people (Judg 11:29), but Jephthah is portrayed as a purely human choice.

I. The Man Rejected (Judg 11:1-3). Jephthah was an undesirable man to lead Israel. He was the firstborn son of a prostitute, whom the Jewish historian Josephus said was a Gentile. Illegitimate sons were not permitted to participate in Israel’s religious ceremonies until the 10th generation (Deut 23:2). David was 10 generations from Perez, the bastard son of Judah by his daughter-in-law (Gen 38; Ruth 4:18-22). Illegitimacy isn’t the fault of the child, still the choices of parents affect their children.
Despised by his greedy half-brothers, and aided by Gilead’s leaders, Jephthah had been driven from home and became the leader of a gang of predatory thugs.
Jephthah suffered for the sins of his parents. He was a bastard, despised by his family, an outcast leading other outcasts. But his background of liability formed him into a man of valor, courage, bravery, strength like Gideon (Judg 6:12). He refused to be a victim of the past. This is often how God works, using the least desired by the world (1 Cor 1:18-2:15).

II. The Man Sought (Judg 11:4-10). Israel’s elders offered to make Jephthah the commander of the army. The ones who made Jephthah an outcast now begged for his help. They would accept him because their need was greater than their hatred of him. To sweeten the deal, the elders offer to make Jephthah their head (Judg 11:11); the Hebrew word used is rosh which means prince. They submitted to Jephthah’s demands and agreed Jephthah could do to them as he wished if they didn’t keep their word. What’s amazing is how this echoes Israel’s rejection of God in Judges 10:6-16 … and Israel’s rejection of Jesus more than a thousand years later.

III. The Man at Mizpah (Judg 11:11). At Mizpah, Israel’s elders publicly swore to God who hears all, sees all, and will hold them responsible, to keep their oath to Jephthah. Mizpah was where Jacob made an agreement with untrustworthy Laban (Gen 31:49). For Jephthah this oath may have been meaningful, but for the elders it was a mere formality. They were using God as politicians often do for an appearance of legitimacy. God would use Jephthah to deliver Israel and give them the leader they deserved. Love isn’t always warm, affirming, or sweet. That’s sentimentalism. Love also teaches hard lessons about sin, responsibility, and consequences.
The once rejected Jephthah became Israel’s prince.
Most preaching turns this passage into being about the hearer, but it’s about Jephthah and the One he points toward: Jesus (Ps 118:22; Is 53:3; Mt 21:42).
Jesus came unto His own (Jn 1:11), was accused of illegitimate birth (Jn 8:41, 48), was hated and rejected by His own family and countrymen (Jn 7:5; 15:18-19). Yet one day, He who came to seek and to save the lost, shall be sought by His own, and Israel shall turn to the fountain opened for the house of David and for the inhabitants of Jerusalem, for in and for uncleanness (Zech 13:1) and He shall reign as King of kings and Lord of lords of all the earth