yes, some children stop stuttering. that's not unheard of, and can happen with or without therapy. but "because it improved after we changed X, X caused it" is a post hoc fallacy. did psychological factors influence the expression of your son's stuttering? sure. did it cause it? no. the only case that would be true is if your son had psychogenic stuttering (a rare form), which is acquired suddenly due to severe emotional trauma, extreme stress, conversion disorder, depression, etc. and just because he recovered with environmental changes does not make it psychogenic stuttering. of course you got silence when you said you wanted to "stop" his stutter. framing stuttering as something that needs to be eliminated isn't healthy and often worsens outcomes for many kids.