There is so much disinformation out there with many people making a mountain out of a molehill. The actual ruling has not been posted on the court web site, so the conflicting stories can not be sorted out.
Even if it was not 9-0 and even if he opposed Roberts, Scalia, and Thomas he still did the right thing. Alito has been on the court for less than 24 hours and he got this case of execution stay that was supposed to expire today. He cannot just go ahead and say yep go ahead and execute the guy without reviewing the case. He needs few days to review it in order to make a sound judgment and this tells a lot about his great demeanour and fairness.