Social media and the ‘media’ generally, (that is films, tv, etc.) have encouraged this. Social media especially, glorifies the ‘maverick’ or rebellious to some kind of BS status in our society and a lot of maladjusted people see this as a confirmation of their views, choices and their conduct, however outrageous it may be.
Their alienation is not the cause of their rage but a result of severe dysfunction in their upbringing. The perpetrators, likely her parents, took no responsibility for their actions and the child, who can't accept that the source of her disorder is her own parents, instead blame everyone else. The parents even fuel such blame because they're unable or unwilling to accept their own responsibility.
One could see the same with almost all such Leftists, some more public than others, like Greta "Scoldilocks" Thunberg.