The Umbrella Academy: What Does The Ending Really Mean?
9. The Academy Caused The Apocalypse (And Could've Prevented It)
A bulk of the season finds the Umbrella Academy waiting for the coming apocalypse, and trying to figure out how they can prevent it. They learn it all hinges on someone called Harold Jenkins, who transpired to be Vanya's love interest, Leonard. When she kills him in episode 7, it appeared to be over, but of course, it wasn't so simple.
Instead, it was their pushing away of Vanya that ultimately leads to the apocalypse. It's not all their fault - Leonard takes his fair share of the blame, and the root cause all goes back to Reginald - but there are a number of occasions when they could embrace their sister and avoid this mess. If Luther hadn't locked her up, then it wouldn't have happened. If they'd listened to her before then even, it might've been avoided. If the rest of them had allowed Allison to approach her at the concert, then it would've gone very differently.
In the end, it was their efforts to prevent the apocalypse, and their fear that Vanya would be the one to cause it, that led to it actually happening. It's an ironic twist, but one the Academy had a number of chances to avoid.