Hello PreparedRug4, first of all welcome to the forum
I have a whole year researching Columbine and here in the forum, I was also very young when this happened and I remember a bit and also remember heard about it years later but till now caught more my attention and Ive been wondering your same question.
What I did then, was to not only analyse the case but also the society of that time and now, I noticed that the 90's could be the most depressive generation for several reasons and everything started to became very empty for young people, this eventually affected my generation and the most recent ones too, which makes many people (including me for example) to feel very related to Eric and Dylan and this particular case.
Why?, well because if you start to read about it, you see that they were not only kids with mental problems but also social problems and problems to accept the system and what the adults teach us, but they were not and they are not the only kids with those problems, in the last generations many have the same ideologies and problems, you can see that the bullying and suicide problem is more serious now and I have seen how many guys are even fascinated with guns and have desires to do the same of Eric and Dylan because they can feel more related to them than with another Mass Murderer. Adam Lanza and the mass murderers who followed after Columbine, are part of this group so anyone pay them many attention, not matter if they killed more people, because Columbine started many things, it was like a revolution, started many debates and is the case with more information in the internet and are involved two kids who seemed very normal just like all those kids seem, so all that makes it more attractive. I even think that after last week, any similar mass shooting with many attention in the media, involved more than one gunman, what makes Columbine even more interesting.
I am not saying that the Sandy Hook case cant not be that fascinating because it could but we are barely starting to know things about Adam and he was another kid of the group who is the result of a society that is each time more fucked up.
Also, as you pointed out, Columbine was not planned to be a mass shooting in general, it was a bombing and became the most traumatic School Shooting in the end, another point of why its so interesting to so many people. I dont think that it would not have the same impact as a bombing because it was planned to be something with a huge impact anyway and as Eric and Dylan wanted and predicted, is a case that started many copycats and each one more traumatic or with more fatalities than the last one.
In conclusion, Columbine is still very fascinating because these generations are full of people like Eric and Dylan, because Eric and Dylan remiend us a way (and not a very good one) to show what bother us of everything (from school system to society in general) and people can still feel related to them and have the chance to know a lot of them in the web for all the tecnology that didnt exist in the 70's or 80's when other mass shootings ocurred and I dont think that this will pass soon, not while what they hated so much and with what they were victims too is still relevant and also still affect many other kids and not while the media still give it attention.
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The most terrifying fact about the universe is not that it is hostile but that it is indifferent; but if we can come to terms with this indifference and accept the challenges of life within the boundaries of death — however mutable man may be able to make them — our existence as a species can have genuine meaning and fulfillment. However vast the darkness, we must supply our own light