It is difficult to understand when someone, who seems perfectly fine on the outside and has so much to live for, takes their own life. The news blurb says, "X was depressed."
Severe depression doesn't have much to do with the much more common feeling of being down, which we also call depression. The symptoms bear similarities, but the underlying causes are completely different. It's a little like thinking that a person with a terrible cough has the flu when they really have lung cancer.
Feeling down is caused by real things happening in the real world. Severe depression is an inescapable, suffocating state of mind where it seems like the simple act of living is a trigger for feeling down. Maybe something bad happened a long time, but it's long past.
Severe depression is a heavy, invisible burden. You can't tell that someone is severely depressed. It's lung cancer that looks like a bad flu. And the sufferer can't tell anyone. It's extremely difficult to understand what's it's like unless you've been through it yourself. Few people understand it. They don't want to hang around with some moody, troubled person who drags them down. But even if a person has supportive, sympathetic friends and family, it doesn't change the hard reality -- the sufferer has to live with painful feelings every hour of every day. Friends help a lot, but they can only carry a little of the burden. The sufferer is mostly alone.
For those people in the news blurbs, maybe there came a time when the burden became too heavy to bear. Unfortunately, it makes all too much sense that any sane person would want to end it all.