You are talking about the impact of ctb on others, right? I don't think it's like a normal breakup at all. Maybe if you were together for years and your lives were completely entwined, then yes, a piece of you dies when that person leaves. However, death is permanent.
I've lost a close friend to ctb, had many attempts in my family, several people I never got to know like aunts, uncles, cousins all ctb when I was very young. So I have a way of viewing and processing death that a lot of people probably don't, because I've been consistently exposed to it since a young age.
I don't blame people for ctb, nor do I think anyone could have prevented it in a lot of cases if the person is hellbent on leaving this world. After my father passed, it hurt terribly, but even as a child I was able to recognise that he was no longer suffering and finally got to have peace from a life of torment.
Watching one of my family members succumb to a horrible illness and go out the natural way was far more traumatizing to me personally than hearing that someone I cared about ctb, because I knew how much pain that person was in.
Grief causes strange and devastating feelings for many people, and out of grief many people see ctb as the worst way a person can go out. Because they want that person back they go over a multitude of possibilities in their heads about how it could have been prevented. I have been in that position, and I realized it wasn't doing myself or my late friend any favors to think about what ifs.