Ibn Abil Hadid has tackled the dilemma of the rulers in his Sharh Nahj al-Balaghah.
He writes:
One of the teachers of Baghdad was asked – Wasn’t Fatima (s.a.) truthful in her claim?
Teacher replied – Yes.
The person asked – Then why didn’t the ruler hand over Fadak to her while she was truthful?
Teacher – If he were to grant her Fadak based solely on her claim, then certainly she would have approached him the next day and claimed caliphate for her husband. And in this way she would have displaced him from his position (as ‘caliph’).
Then it would no longer be possible for him to offer an excuse as he had already noted that she was truthful in all her claims.
Ibn Abil Hadid mentions that this dialogue is correct.
• Sharh Nahj al-Balaghah v 16 p 284
• Ithbaat al-Hudaat v 3 p 410