How did Christensen gain control of the broadcast?

Diana Christensen is the head of scripted television at UBS. She is a relentless professional and her work is her life, and getting UBS to number one is what she desires. She convinces Hackett to give her Max’s job producing the news in order to raise ratings and bring the network out of the gutter, which she does by placing Howard Beale right where he shouldn’t be...in front of the camera, and letting him say anything that comes to his mind. Her plan begins to work, and she is hailed as a conquering hero by her network cronies until The Howard Beale Show begins to dip in ratings. Once there is the potential that she will lose ratings, she is willing to do anything to save her career and the network share, and is complicit in Howard’s murder.