Erin Brockovich is a woman without too many opportunities. She has high ambitions, at the same time as she wants to take care of her children. She is constantly applying for jobs, but doesn't really has any resume. One day after applying for a job, she is being seriously injured after a car accident and hired Masry and Vititoe to represent her in the lawsuit. Later on she also got a job here as a file clerk, where she found some medical records that would explode into the largest direct action lawsuit in US history. She has a strong and great personality which pushes her forward in life. But because of her personality and the way she worked, she got fired. But she gets the job back because her boss thinks that the case she is working on is interesting and that he can make quite a number of money if they win the case.
She wants to be something in life, one that makes a difference, at the same time as she has some serious problems at home. But her neighbor helps her out, by taking care of her children at daytime. She starts to work on the case of Hinckley. The PE&G lets toxic hexavalent chromium into the groundwater, while they say that it is just chromium and that it is not unhealthy. This caused dangerous illnesses for many of the people in the town, and Erin tries to reveal the secret by talking to families who are affected.
In 1996, because of the largest direct action in lawsuit US history with Erin Brockovich and Ed Masry in the head of the investigation, the utility giant was forced to pay out the largest toxic tort injury settlement in US history: 333 million dollar in damages to more than 600 of Hinckley's households.
In my point of view the reason she managed the task was because she cared for the people that lived in the town. She could not stand watching all those individuals suffer, just because the utility giant wanted to earn some extras. She also had an incredibly heavily energized to trap the company.
The reason why "Redemption Day" by Cheryl Crow is used as the theme song, i think is because it describes what happened very well. Especially the first verse tells us what Erin felt about the whole case, and what she tried to do about it.