To be annoyed about this question

I think it's part blurting out their first thought, part not knowing what to say and part genuinely polite conversation. I don't think it's necessarily rude.

If you don't want to share details, I think something vague like "it was sudden" or "they'd been ill for a while" should suffice. More questioning at that point would indeed be rude.

I know how you feel, a close friend of mine died recently and she was quite a private person and I don't think she would have liked everyone knowing all the details. Also she was very obese and the way she died was related to that and I know she would have hated people judging and it's been quite hurtful to me too a couple of comments have sounded a bit like well what did she expect which is maybe true but also upsetting because it still hurts.
I think it's a normal question for people to ask though but it you don't feel like going into details just say that.

Sorry for your loss OP. Personally,this question wouldn't annoy me,but that's just me, everyone reacts differently. The comment that DOES annoy me when someone has died is when they ask how old they were,and I say for example,75,they 'Oh they had a good innings'. Really? I don't actually think that anything under 80 is particularly old nowadays.

I think maybe this one depends on what did happen. An illness which people would recognise would almost always been mentioned by name, something more obscure maybe still referred to but not named. Sudden deaths involving accidents or other catastrophic events I can see it would vary widely in what people would say/announce. The "what happened!?" question is a natural reaction I think, but the way it is received would depend on many factors. What would be definitely rude would be to pry beyond that, and you'd hope most people would sense if it was going to be a unwelcome question in the first place and stop themselves asking (although clearly not in all cases, I'm sorry op ☹️).

I'm really sorry for your loss, life can be so cruel sometimes xx

So sorry for your loss it is truly heartbreaking. People are usually shocked when its unexpected so say it automatically. I'm sure nobody means to be offensive or to pry

So sorry for your loss 💐

I think it's a "natural" question and not meant to be hurtful.
Also, talking about what happened is a big part of the grieving process, but of course only when you're ready you can't be forced to talk or even think about it when it's too raw.

I think it would depend how close I was to them. A very good friend or relative, I'd probably ask. A casual acquaintance, I'd offer my condolences and assume they'll tell me if they want me to know.

I think it's weird not to tell.

Of course someone is going to want to know what happened to their loved one.

I'm very sorry for your loss, but I don't think people are trying to intrude. I think they're simply trying to show interest and concern, and maybe they don't know what else to say.

Some people will want to talk about what happened to their loved ones. Some people won't. There isn't any right or wrong in this.

If you would rather not discuss it, I think the vast majority of people would respect a simple "I'd rather not talk about it please".

I'm so sorry for your loss. Humans natural reaction is curiosity, and rarely is there animosity attached.

I'm sorry for your loss.

This question is a common reaction, and a natural, empathic one.

If people are vague it's usually because someone's committed suicide. If the death is due to an illness or accident it's often stated.