However, murder-spree Old Joe is too far gone to turn back. When he finally tracks Young Joe to Sara’s farm, it becomes clear that Old Joe’s selfish ambition is the exact incident that ironically enough creates The Rainmaker; in Old Joe’s timeline (more on that later), rumor has it that as a boy, the Rainmaker saw his mother murdered by a looper and had part of his jaw shot off: horrific acts Old Joe nearly commits.
But Old Joe’s alteration of time means that there’s a possibility for more than one path – so when Young Joe finds himself in a moment where his violent ways can’t save the day, he makes a choice to not be like Old Joe and actually give up his all-important ambition to hold on to “what’s his.” He removes himself (and all the bad Old Joe’s done) from the equation by killing himself, thereby possibly sparing a lot more people times of pain and darkness under the Rainmaker’s reign (presuming Cid grows up to be a healthier, nicer, all-powerful guy).
Time travel stories are tricky; there always seem to be loose ends left dangling, and/or connections that don’t quite add up. Looper, unfortunately, suffers this problem as well.
The biggest issue, as always, is the multiverse factor: if a guy from the future comes to the past and starts mucking with history, it either A) creates a separate timeline that runs parallel to the original one (allowing for two versions of history), or B) The actions in the past forever alter the flow of a single timeline, allowing for just one version of events. Looper plays fast and loose with this time travel mechanic, at times relying on both single timeline and multiverse timeline approaches to push the story forward.