N is cupbearer to a king a long way from Israel, but he is Jewish. He hears that a remnant of the exiles have been allowed to return home and that Jerusalem is broken down and a mess.
He prays. For him, the history is a spiritual consequence. Totally links the scattering of the Jews to unfaithfulness. With repentance, he calls on God to forgive him his personal unfaithfulness and remember his promise to Moses that if the people return to him he will gather them and bring them back.
N’s prayer is deep, it is associated with days of weeping and fasting. As soon as the news of Jerusalem reached him, he knew it was a turning point.
N’s part in the promise is recognising that God is king, promising obedience and faithfulness.