The problem that isn't addressed is why these "bullies" are acting in such a way on tumblr, a medium that allows for anonymous asks and messages, and for people to send "fan mail." While it's disturbing that the atypical hivemind is at work (mob mentality), the better question is why all these people choose to act this way on the internet - and more than likely do not in real life within the concrete public space.
Most likely these individuals act in an abusive manner in order to release whatever stress levels/real life issues that they refuse to look at or try to solve. In actuality, they should be seeing/talking to a therapist or psychologist, since it can be construed that their parent(s) are not in the picture.
It's very easy for [ignorant, stupid, misguided, immature, angry] people to get whipped up into a mob mentality. Sure, it's a sad case of driving someone to suicide or attempt it - but this won't be the last time this occurs, on tumblr or anywhere else.
I get what you're saying here. As you said, the most likely scenario is that they use it as their form of release from whatever may stress them out. Doesn't justify it, though. I wouldn't go so far as to say they would need to talk to a doctor of some kind, but I'm sure some are better off. I think a lot of people are just misguided and follow the pack, even though they believe they are 'being themself and no one else'. A lot of it could probably be avoided if they got a hobby that didn't involve the internet. Just something to cut that connection every once in a while.
There's also the feeling of being justified. I haven't researched deeply into the ordeal, but many felt that zamii was making "problematic art", therefor, she deserved whatever she got. Looking at the one YouTube video comment section alone, she was labeled as racist, so what was done with the intention of higher morality became a toxic circle jerk and a witch hunt. What makes the situation so disturbing (and scary) is that many of the attackers felt that they were in the right. They were "calling out a racist and problematic person" without realizing that they were being even more horrible.
It's basically a case of: good intentions - terrible results.
It may be good intentions, I can't speak much about what Zamii has created and/or done. However, I have seen quite a number of times where tumblr calls something out as racist, when they are just severely misinformed.
I wish I could find the original, but there was one post in particular. A female German cosplayer had done a cosplay of Garnet from Steven Universe. Very, very well done. It included full body paint to fully realize her transformation into the character.
Then along comes tumblr, calling her out for practicing Black Face.
Based on the image that they provided? It is not Black Face. I'm not sure they actually know what black face is. Black face is in poor taste and a caricature. The cosplay in question was very tastefully done, and in no way offensive when looking at it. Not to mention the fact that, oh, I don't know, that the body paint and Garnet herself are more of a reddish/purplish tone.
But then, if she had cosplayed without the body paint, it'd be PoC erasure.
You can't win with those kinds of people.