San went into the diner to get pie for dean. Sam got kidnapped by yellow eyes. Sam got killed. Dean sold his soul. Dean died. Dean started hurting souls in hell. This started the apocalypse. Conclusion: the apocalypse started because Dean wanted pie.
Why is everyone not a part of this fandom? It's literally perfect. <--This. I would also like to add even if there was time to explain I would still get on the Dean<----PREACH. and everybody should be in our fandom. were just that epicaltastic.