https://www.gamespot.com/articles/luigi-is-not-dead/1100-6461042/

During the Super Smash Bros. Ultimate presentation today, Luigi was brutally struck down by Death. His soul left his body. Some took this to mean that Luigi had been officially killed off.

He was not. Nintendo has since confirmed that "Luigi is okay" in the wake of his most tragic and painful event. That's good news, because Mario's unlucky brother deserves a break.