But there is a substantial link between dropping caffeine and sleeping better. And there is a link between sleeping better and getting more effective exercise. And it is hard to get effective exercise and still manage to live on something like Mountain Dew (which might prompt an improved diet).

True - if caffeine was interfering with his sleep then it was a problem. I didn't see any indication that he had attempted to fix his sleep schedule before he dropped caffeine, though it's certainly possible that he did. Sleep exercise and diet are connected to each other, and maybe kicking caffeine happened to give him enough motivation or momentum to improve all three of them, but it's only loosely related. Setting up dropping caffeine as the cause of his improvement is strange - it just happened to come first.

You're correct about not trying to fix the sleep schedule before kicking caffeine. I was just too damned busy, for far too long. Cf my above comment about caffeine's continuous nature, too.