I remember the speculation around town at the time, but never gave it much credence. But I just watched a film on Netflix called "Soaked in Bleach" that makes a credible case that Cobain's death was a murder staged to look like suicide.
There's no doubt that his widow was (is) one seriously-damaged human being, but it's a long leap from self-absorbed drunk to murderer. I was skeptical going into this documentary. She was out of town when it happened, so it would have had to have been contracted. But the evidence is pretty compelling that she orchestrated it.
She was the one who hired the private investigator to "find" the missing Cobain, and told him she was worried that Kurt had been suicidal and that his credit card had just been stolen, both apparently untrue. She called in a missing-person report under the name of Kurt's mother, making it sound as though the mom also believed him to be suicidal and "had a shotgun". She claimed Kurt had three uncles who had committed suicide - also untrue. She claimed that he'd attempted suicide once before, another lie.
It all sounds like an alibi/explanation in the making.
The evidence is carefully and systematically laid out in the film, making the case that the police investigation was badly botched, that not one friend or family member thought Kurt was suicidal, that physical evidence contradicts the official scenario. Their own lawyer believed the suicide note was a forgery (agreed to by a handwriting expert and a forensic linguist), and knew that Kurt had just asked her to help him with a new will that Courtney was cut out of.
A divorce was in progress that would have left Courtney with very little due to a prenuptial contract, but because he died before the divorce was finalized, she got hundreds of millions and continues to rake in money from royalties. No motive there.
It would seem that the public and police were too quick to accept the suicide story. After all, everybody knows that rock stars only die one of two ways: drug overdoses and suicides.