He did. And intentionally. Jor-el told him that if he went back in time, universe would find a balance. Someone else would die. He doesn`t even think.He just goes and say "I have to do this"
A hero doesn`t chose a life over the other. A hero choses both. Thats why even Spider-man didn`t chose MJ over the kids in the movie. He saved both.
So, it was, to me, a terrible written episode. In that episode, Lana shouldn`t have died, should`ve know Clark has powers, not get married, no bul**** like that and his father should`ve died of natural causes like in any Superman story.