I'm not diving into the splits..but I figure their pitching has been mostly good the entire time. The offense is catching up.
Here's the real question, were all of the losses in leveraged situations a fluke, bad luck? Can they have a normal reversion to the mean and close a few tight game when it matters? If they can, then the run differential will matter and they will win the division.
Their defense has improved to mediocre over the course of the season..if you are looking for another reason for the surge.