The question at the heart of the matter, frankly, is why Ally waited so long to act against Kai. As Reddit user fortheloveofsyd asked, “Why couldn’t she [Ally] have called the FBI earlier rather then wait for “innocent people” to die along the way? I feel like Kai held meetings often and she could have gotten the FBI to raid then earlier on. Maybe I am missing something. I guess the raid could have been delayed to drag out the season as well.”
In response to this, DonnieDarkoRabbit pointed out Ally had her own agenda regarding Kai and his cult. “She [Ally] played her time, though. She first wanted revenge on Winter for ruining her marriage and convinced Kai to kill her himself, and he’s certifiably crazy. She wanted the therapist dead for letting Kai get access to her secrets. She wanted Ivy dead for obvious reasons, except she killed her herself as a power move,” they responded.
In “American Horror Story’s” Season 7 finale, Ally tells Beverly Pope (Adina Porter) the FBI offered her immunity to infiltrate Kai’s cult. That means Ally had a free pass to execute her revenge plans. Not only could she blame Ivy’s death on Kai, but she manipulates him into killing Winter, who had as much of a hand in trying to destroy Ally’s life as Ivy. In the end, Ally alerts the FBI before Kai and his army can attack truly innocent people (100 pregnant women).