Why did Grindelwald laugh when he told Voldemort that Dumbledore got the Elder Wand?

You're likely referring to a scene from the "Fantastic Beasts: The Secrets of Dumbledore" movie. Grindelwald *doesn't* actually laugh in that scene. He seems almost amused, but he doesn't laugh. He states the fact that Dumbledore obtained the Elder Wand with a calm and somewhat smug demeanor.

Here's why this scene is important:

* Grindelwald's pride: He's very confident that he's the only one who can wield the Elder Wand effectively. He likely believes Dumbledore will be unable to master it or that he can eventually reclaim it.

* Understanding the true power of the Wand: The scene suggests that both Grindelwald and Voldemort were unaware of the Wand's true power, which lies in the allegiance of the previous owner. Grindelwald seems to be surprised when Voldemort asks him if Dumbledore can truly use the Wand, implying that he, too, underestimated its power.

* Setting up a conflict: This scene establishes a new kind of conflict between the two powerful dark wizards. They are both vying for the Elder Wand, but in a very different way than they initially thought. It also adds another layer to the complicated relationship between Dumbledore and Grindelwald.

It's important to remember that the movie is a loose adaptation of the "Harry Potter" lore and might deviate from the original canon in some aspects.