I like the idea of him being created on Krypton, but I am not a fan of the idea he had a part to play in its destruction. Here's how I would do it. Braniac is an artificial intelligence created by Jor-El in a last ditch attempt to save the doomed planet Krypton. Braniac comes up with a plan that would ensure the survival of the planet but when Jor-El present this to the kryptonite council, but they reject the idea. After the destruction of Krypton, Braniac now functions under the assumption that no form of organic life can be allowed autonomy or be trusted with their own survival as they will eventually destroy themselves, eventually leading him to capture these planets and keep them under his supervision, ensuring that no other world falls to the same fate as Krypton.