Theories, my view.
Or she actually found out she is an NPC in a virtual world. When she traversed the “Eternal Alchemy” she actually got a glimpse of our world. And the “thing” that stared back was actually just a developer playing galaga at the time.
She refused to accept she was just an unsignificant virtual character in a video game so she vowed to destroy as much of the game as possible, starting at the core (Lions Arch), hacking parts of the game along the way to make her unrealistically smart (which drove her insane).
…
Yes I am joking, but it’s a funny story if I say so myself
Dear A-net: Please nerf rock. Paper is fine
~Sincerely, Scissors
~Sincerely, Scissors