Allah decided to send the Prophet Nūḥ to Earth because the descendants of Adam, after having worshiped Allah for a long time, began to worship idols and saints. Out of mercy for his people, Allah sent Nūḥ to remind them of the truth. He chose Nūḥ to convey His message, as only Allah knows who is worthy of carrying His message and who is truly sincere. Nūḥ was a pious and charitable man.