وَ«قَعَدْتُ عَنِ الْحَرْبِ جُبْنًا» أَيْ لِلْجُبْنِ.
Translation: And: I stayed away from war out of cowardice—that is, because of fearfulness/cowardice.
Here jubnan expresses an inner cause/motive, not necessarily an outcome being pursued. “Why?” can ask about motivation as well as intention.