Why did the author choose to reveal the evens of the story in this order ?

The story begins in flashback with Madame Valmonde visiting Desiree and her baby. On her way to L’Abri, she reminisces about Desiree’s childhood. THe narrative then proceeds in order of events until Chopin uses a "trick ending". Undoubtedly, Chopin was familiar with the surprise ending. She was an admirer of the works of Guy de Maupassant, and his story, "The Necklace," uses a surprise ending for tragic results. Indeed, "Désirée's Baby" too results in tragedy for all involved. Désirée and her child end in certain death while Armand discovers that the "African American blood" evident in their baby stems from himself. The ending demonstrates the irony and the ambiguous nature of racism.