Why was the Mus'haf (codified copy of the the Qur'an) placed with Hafsa, and remained with her until Uthman ibn Affan requested it from her?

To begin, Abu Bakr compiled the Qur'an after a large number of Qur'an memorizers were martyred in the Ridda wars, and the Companions approved of this. After Abu Bakr's death, the Qur'an remained with Umar, who then bequeathed it to his daughter Hafsa. When the Muslims differed in their recitation of the Qur'an, Uthman requested the Qur'an from Hafsa, made several copies from it, and distributed them to the major cities, and the Companions approved of his action.