Nathaniel Hawthorne became interested in making Greek myths accessible to modern children. Before the mid nineteenth-century, they were considered suitable for adults. One main reason he changed them considerably was to render them less frightening and graphic.
For Pandora, he did this by toning down the content and making her a child with a male friend rather than an adult with a husband. The evils that rush out are still pretty horrible, stinging buglike monsters. But he also gave more time to Hope as a character who converses with the children. And the story's narrator says, in essence, I am glad she opened the box because Hope is so wonderful. The story is subtitled Paradise for Children.
Another change was framing. Hawthorne added a framing device of a student named Eustace Bright, who is supposedly telling the myths to a group of children. This change would have made the stories more relatable.