Maybe a million other things happened that might have "turned" Cid.
I though the point of Cid was that unless something changed he basically had already nearly turned into the Rainmaker as a result of unintentionally killing the woman he thought was his mother and the ease with which he could be provoked into a level of uncontrollable anger toward his real mother that was dangerously close to lethal. Cid in many ways is already almost as fallen and thoughtlessly willing to pull the trigger as Joe is when we first meet him, and already nearly as bent on the impulse driven destruction of others and ultimately himself as the Looper's job, lifestyle and contract makes them.
So the question the movie posed for me was what does it take to turn any of these characters away
from being what they already are, a Looper or a Rainmaker. The movie suggests that breaking the sinner's Loop to turn away a bad future takes a lot, including sobering up, the willingness of Young Joe and Sara to offer or sacrifice their lives to protect another, the renunciation of the world (the silver/gold and future promised by old Joe), and young Joe's rejection and in a sense repentance from the ever escalating sinful means old Joe has embraced to acheive his "solutions".
Anyway, I don't think the movie left the question about how Cid became the Rainmaker in the original timeline unanswered. Cid is already an alienated timebomb that could go off at any moment unless something defuses him by the time Joe meets him. The death of Cid's real Mom by either his unchecked powers or by Old Joe is what seals his Rainmaker fate, and the actions of Cid's Mom and Joe seem to break both of those cycles by the end of the movie.