Does anyone know how Moroni died? Was he changed in a twinkle of an eye, as many prophets before him, or was he killed by the Lamanites?
There’s really no way for us to find out the answer unless Heavenly Father reveals it to us directly.
Moroni received the plates from his father, Mormon. Mormon was later killed by the Lamanites as recorded by Moroni. Because Moroni hid the plates before he died, there’s no record of how his life ended. It is possible he was translated, and it is equally possible some Lamanites found him and killed him.
When Heavenly Father gives a prophet something to do, he protects and guides them to make sure what he asked of them is accomplished. After their mission is done, some prophets are translated, such as Elijah, and others are killed, such as Abinadi and Joseph Smith.
It’s an interesting question, but unfortunately there’s no expectation for an answer any time soon.