I think it was power of hipnosis like suggestion. Your belief that it will help came through in your tone of voice and body language. The boy got distracted.
Consider this: I was in a car with a little girl throwing a crying tantrum. After a while I turned around and touched her knee and asked her gently to stop.
She stopped immediately, because touching her was distracting and my speak too. That got her confused and she was distracted. After several seconds she realized that now it wouldn't make sense for her to start crying again, lol.
Other people present said it was "magic", but it's just psychology.