Mr. Krabs did not actually die in the official SpongeBob SquarePants series. The rumors about his death originated from a fake, fan-made document called "The Trial of SpongeBob SquarePants," which presented a fictional story that Mr. Krabs was found dead inside the Krusty Krab with his throat cut by a metal spatula and evidence of blunt force trauma to the head. This document sparked theories and speculation among fans but is not part of the show's canon. Officially, Mr. Krabs remains alive and active in the series.
In summary, no real death of Mr. Krabs has occurred on the show; the story about his death is a piece of internet lore and creative writing rather than an actual plot event.