Thanks for that follow up, Arta.The article, like the one at The Intercept, is about it being a "surprise" vote though it does not go into nearly the detail of 'why' it was is a surprise.  McCain's explanation might even be the real reason for his vote but I do not believe it can be taken on face value just because he said so. [He is a politician] My speculation is that Davis Dayen 's speculation at The Intercept provides the  most likely explanation of the two. McCain is, IMO, a damaged person with tremendous anger management problems. Sometimes he pulls the trigger before his gun clears the holster. That has been demonstrated over and over through the years since he was released fro a POW camp in Vietnam. Usually though when he goes red in the face and starts screaming it is because he wants to sanction some country or drone murder some leader or else bomb their whole damned country. I doubt he was livid over the legislation as he screamed at Cornyn and a couple other Republican Senators just before he cast his vote against their wishes.

McCain’s conduct during the Senate vote also raises red flags. In the C-SPAN video of the vote, McCain can be seen in heated discussion with John Cornyn, R-Texas, the number two man in the Senate leadership, along with John Barrasso, R-Wyo., and an unidentified senator with his back to the camera. After yelling at them for close to a minute, McCain goes over to the Senate clerks and gives a thumbs down to record his vote. He then storms out of the chamber, as Cornyn raises his arms in mild protest. 

Because the bill he voted against was one which removed some environmental protection, it is not hard to come up with a contrived excuse, if necessary, that sounds perfectly sane to justify an anger inspired rash action against his own Party's intention. I have not heard that he campaigned against the bill before his vote. It is close to certain that some republican Senator changed his mind after the whip count assured that the bill would pass. My bet is that it was McCain.