If someone died suddenly, you wouldn't have had time to ask them if they were OK with you discussing the cause of their death with all and sundry! So talking about the cause feels like you're sharing someone else's private story without permission.
If you want to ask about the cause of death - why? Is it really out of concern, or to satisfy your own curiosity? If for your own curiosity, there's your answer - it's not about you.
When it comes to death, all you can do - all you should do - is support the people left behind. If they want to tell you the details, fine, but it feels like an intrusion to ask for anything they don't want to volunteer.
I hope I am not going to offend anyone here I just find it sad to be so invited emotionally into a lost life and human nature means you are going to purely internally speculate on what has happened to the person who has sadly died.
The short answer is human nature is horrible. Truly, I'm not judging you, I'm judging us as a species (which naturally includes me). You're right, we will wonder... but we should suppress that instinct to make it about us, and to make it about the grieving people instead.