Board Thread:Fanon Canon 2/@comment-2185383-20140924182221/@comment-2185383-20140928013559

As the Hokage, Hiruzen is pledged to protect the villagers from whatever threathens them. The Uchiha clan were still Konoha villagers even if they were planning to overthrow him, so allowing the massacre to happen would mean he clearly failed at his job. I honestly can't see any Kage sleeping well at night knowing some of their villagers, especially innocents, are going to be murdered in cold-blood by their own subordinates. So, this is basically Hiruzen's justice in trying to at least save one of those innocents from the bloodbath, with Kimi being the "lucky" chosen one. Sasuke doesn't count because his survival wasn't even his doing, it was a condition proposed by Danzou, the one who orchestrated the massacre itself.