I have a couple points I'd like to make on this issue, especially as to the types of complications that prevent loved ones from intervening or officials from offering help to the bullied and why punishing "bullies" is often very difficult.
The extent of bullying and its impact on the victim is largely hidden.
Consider a bullied student on a typical day. A couple people on the bus laugh at him and call him names. He gets his books knocked out of his hands between 1st and second period. In third period, someone steals his pencil from his desk. In fourth period, a larger boy hits him on the head with a soft rolled-up folder when the teacher is distracted. In fifth period, a girl calls him a "retard" when he bumps into her in the hall. In gym, a couple kids gang up on him in the locker room and force him to sniff their dirty underwear. Later, a couple girls give him mean looks as he's walking between classes. In science class, when the class chooses lab partners, no one is willing to work with him. At lunch, another kid pours chocolate milk in his mashed potatoes.
Other students and even teachers see this, sure, but most of these things are small and not a big deal, and no one except the bullied students is witness to all of these incidents. Even the ones doing the bullying don't know the extent of the harm being done. These types of things happen to everyone, and anyone should be able to shrug them off and go about their day. The bullied student however, is facing a constant barrage of assaults on his self-esteem and well-being. The cumulative effect of physical and emotional attacks and ostracization becomes psychologically devastating. And what recourse does he have? Demand the principal suspend kids for giving him dirty looks? Throw fists at everyone who crosses him and likely face punishments of his own?
The same is true online. The attacks usually come from multiple sources at different times. Rarely is this a coordinated effort. It's just kids taking pop shots at an easy target. The pain is being dished out intermittently in small doses from several sources, but the target is absorbing all of it constantly.
The "bullies" usually aren't stereotypical "bad apples." There will be a few actual bullies who stalk and attack a victim, but most of the punishment is being dished out by regular students at random intervals. One "bully" might have called the victim a name twice this year. Another may have taken a shot at him once or twice or joined in with a couple of others to make of fun of him a few times; mostly he just ignores the victim and doesn't have any particular ill feelings toward him, but every once in a while, he has a little fun at the bullied boys' expense. These "bullies" are really just normal kids in a culture where they can get away with that kind of behavior sometimes. Even the bullied kids themselves are usually guilty of the same sort of behavior.
But this only adds to the victims' hopelessness. He's under constant assault, and he never knows where it's going to come from. He navigates daily through a hostile environment where the authorities are unwilling and unable to protect him. He has no agency and very little recourse. The fear, animosity, and feelings of worthlessness build, and he faces them with little empathy or support. Everyone knows he's getting picked on, sure, but the incidents are all minor and inconsistent, and no one except the victim is privvy to the full extent of the abuse. It's death by a thousand cuts.
I realize I'm conflating physical bullying and cyberbullying, but I believe the core issues are the same. The problem is cultural. The only way to address it is through institutions that actively work against the culture of bullying. Punishing kids who post a mean message on SnapChat is a poor solution and just creates more victims. Singling out the bullied student for protection (or, worse, suspicion) will just reinforce his isolation. You need a broader approach that encourages bystanders to push back against bullying behavior when they see it and a specific protocol for bullying victims to get help.
Sadly, the Internet complicates this by broadening the bully culture beyond school grounds, but the core problem is still a culture withing the child's community (usually a school).