While Kelly Grayson changing the timeline is what created The Orville’s dark alternate timeline where the Kaylon ravaged Earth, it wasn’t totally her fault that events went so badly. After being pulled forward in time, Kelly’s younger self was left with memories of the future, ultimately choosing to avoid the heartbreak of her marriage to Ed Mercer. This decision had a knock-on effect that empowered the Kaylon in their war on biological life, but it turns out Kelly could have avoided that forbidden knowledge in the first place.
After being returned to her own time, Kelly was mind-wiped by Doctor Claire Finn, but sadly the procedure didn’t work. While Kelly went on to act on the future knowledge she possessed, it was almost unavoidable she’d end up changing history, as it would be impossible to live the same life while knowing how major but not minor events turned out. However, this didn’t need to be a problem, as Claire’s mind-wipe would have worked if she’d caught a flaw in the procedure.
While the error that kicks off The Orville‘s alternate timeline is mentioned in retrospect on the show, The Orville: Digressions (by David A. Goodman, David Cabeza, and Michael Atiyeh) shows the changes Kelly actually made and how their consequences started out. After Kelly’s decision not to be with Ed results in him not gaining his prior position on the Orville, Claire (who likes to be stationed where she’s needed) requests to be assigned to a different ship, meaning that she never falls in love with the Kaylon emissary Isaac, influencing his affection for humanity. Isaac therefore has no reason to betray the Kaylon, and their plans are successful, allowing the massacre of Earth and a far stronger presence in the galaxy. After Kelly sets out to unite the Orville‘s original crew, she has Claire look into why her mind-wipe didn’t work, and it turns out that the doctor’s screening missed a beta-secretase deficiency that explains why the procedure didn’t take. In the comics ‘prequel,’ Doctor Claire Finn is particularly upfront that she’s responsible for failing to catch this problem the first time.
Given the heroics of the Orville crew just to place Doctor Finn in a position where she could take the fateful step of erasing the younger Kelly’s memory, this is a pretty glaring foresight by a trained medical professional. Ever quick on her feet, Kelly does find a way to undo her greatest failing, but a huge amount of suffering results before the timeline is restored. With the stakes being as high as they were, Claire needed to go the extra mile in ensuring that the necessary conditions for a successful mind-wipe were met. It’s particularly telling that once she knows the mind-wipe didn’t work, Claire detects the problems quickly and definitively, showing it was always possible to identify.
Like Star Trek, The Orville takes the responsibilities and actions of its heroes deathly seriously, and Doctor Claire Finn made a major error with this oversight that almost resulted in the death of all biological life. While Kelly will always live with the knowledge that her younger self made the potentially disastrous decision to change history, equal blame falls on Claire, who as the Orville‘s trusted doctor failed in a major way that it’s unlikely she’ll ever have to confront.