Why does Cyrus spare Croesus's life in "As Rich as Croesus"?

Cyrus spares Croesus' life when he realizes he is an ordinary man. First Cyrus orders that Croesus burns to death on a pyre because he wants to prove that he has supernatural powers that would prevent him from burning. Then Cyrus changes his mind. However, his servants can't put out the flames, so Croesus prays to Apollo and a storm extinguishes the fire.

In the end, Cyrus is certain that Croesus is a good man and makes him his advisor.