OP you’ve been through something horrendous and a lot of people (some who really should have known better) have made really unhelpful, uninformed and judgemental comments. Of course it’s hurtful, of course it makes you angry. YANBU. Now you are seeing similar comments being made about a news story and it’s dredging everything up. You have my every sympathy.
I too have been in a similar position and had to listen to people making these comments. You asked why people do it. After many years of pondering the same thing these are my thoughts:
Misplaced guilt - it’s very common for people to feel very guilty when they lose someone this way. It’s usually totally unnecessary guilt but all the same it’s a horrible feeling that eats away at you. I think sometimes people try to ‘project’ their guilt away onto somebody/something else so they don’t have to feel it anymore.
Misplaced anger - it’s normal to feel irrational anger when you’re grieving. It’s also normal to feel anger at a loved one who has taken this awful decision. But then you feel awful about being angry at them so, again, you project it all elsewhere. Looking for someone or something to blame.
Fear - it’s very frightening when a person dies in this way. People try to comfort themselves that it would never happen to their loved ones because they would do it all ‘correctly’ and ‘save’ them. As you have pointed out, this is not always possible.
Have you ever noticed that when, for example, a person gets a cancer diagnosis, some people say really unhelpful things like ‘oh are they a smoker?’ ‘is it because they drink too much?’ Etc. it’s the same sort of thing. They are trying to comfort themselves with ‘I don’t smoke so this won’t happen to me’.
Sorry for the long post but I’ve thought about the same things that are troubling you for a long time and I hope you might find this helpful. They’re all trying to make themselves feel better in clumsy ways, none of it is your fault.
Take care of yourself.