Trump lost his #1 political adviser over this (his only adviser with experience in Presidential campaigns):
http://www.politico.com/story/2015/...-donald-trump-in-campaign-shakeup-121177.html
Then, just as tried to lie about not implying that Kelly was menstruating, he tried to lie by saying he fired Stone (not that it really matters why Stone left).
It's not hard to figure out what happened (it's perfectly in line with the account from Stone and his friends). Stone actually wants to win this thing. He has a genuine ambition to win. And he laid into Trump with the exact same point raised in a rhetorical question earlier today put to all Republicans by Jeb Bush at the Redstate convention:
Trump brushed him off by citing the Drudge Poll. Stone, not being an idiot like the other neophytes in Trump's campaign, wanted him to understand that short term laughs don't ultimately equate to votes after the very long term campaign. He's understands things like controlled polls, net favorability, demographic awareness, etc. When he realized Trump didn't care about doing what needs to be done to win, rather than just soapbox and rabblerouse, he split.