Monsters.
They had been led to believe by those who raised them, including their mothers, that they were sooo special that they were going to enjoy semi-god status all their lives. And when this didn’t happen, for reasons relative to their behavior or not, they couldn’t stomach the situation and lashed out to those whom they perceived as being the culprits.
So it’s not only their upbringing, it’s just that their upbringing didn’t do anything to tame their overgrown and misshaped egos.
And that’s why I believe they are monsters, deformed beyond their individual capacity to deal with their deformity.
Interestingly enough acid attacks are not a modern occurrence nor perpetrated exclusively by men:
“Vitriol appeared in Europe during the 16th century, and a recorded case of an acid attack occurred in 17th century France under the rule of Louis XIV (Bodnar, Rougo, Grolleau et al 4). Many reports suggest vitriolic attacks were in vogue during the late nineteenth century in the United Kingdom and Europe (Guillais 149; Shapiro 79; Harris 238; Hartman 239).
A ‘wave of vitriolage’ occurred, particularly in France, where in 1879, 16 cases of vitriol attacks went before the assize court; and from 1888 to 1890 there were 83 reported cases (Hartman 240; Guillais 149). The rhetorical and theatrical term La Vitrioleuse was coined, and their violent acts were widely reported in the popular press as ‘crimes of passion’, perpetrated predominantly by women against other women, and “fuelled by jealousy, vengeance or madness and provoked by betrayal or disappointment” (Shapiro 139).”

“IT WAS LIKE BURNING IN HELL”: A COMPARATIVE EXPLORATION OF ACID ATTACK VIOLENCE