Jephthah had been expelled and disinherited by his brothers (apparently after their father’s death). This led to his questionable way of life as a leader of a band of raiders, which in turn resulted in his ability in warfare and made him the right man to lead in battle. So, while on the one hand he was the obvious candidate for commander, on the other hand he felt rejected and isolated from his community. The latter led to his reluctant attitude when they approached him and the subsequent difficult negotiations.
7 Jephthé répondit aux anciens de Galaad: N'avez-vous pas eu de la haine pour moi, et ne m'avez-vous pas chassé de la maison de mon père? Pourquoi venez-vous à moi maintenant que vous êtes dans la détresse?