On the surface, it would seem that Abigail is the primary cause of the accusations, the hysteria, the trials, and everything that leads to Salem's downfall. However, Miller shows that it is the culture of Salem, not Abigail, that is to blame for all of these things. Abigail and the other girls are being mischievous in the woods as adolescents do. When they fear the retribution of their fanatic, religious elders, they agree to make up stories about witchcraft. It is the strict religious culture of Salem, not the actions of the girls, that leads to the hysteria of witchcraft.
Abigail has no parents. Parris provides for her but seems to give no emotional support or affection. Therefore, Abigail acts out (with the other girls) and she seeks affection from other adults, namely John Proctor. While Abigail does do malicious things, she is a product of her circumstances and the culture of Salem. It would be easy to condemn Abigail but considering the lack of parental guidance and love she's gotten, she deserves some sympathy. She acknowledges this in Act One during her conversation with John:
I never knew what pretense Salem was, I never knew the lying lessons I was taught by all these Christian women and their covenanted men! And now you bid me tear the light out of my eyes? I will not, I cannot! You loved me, John Proctor, and whatever sin it is, you love me yet!
Other than John, who eventually casts her aside, Abigail never gets the support/love she needs from Parris or anyone else in Salem.