Oh, that. It's actually pretty simple. China has and dedicates far more money and might than any (all, really) of the other claimants to the various islets and reefs in the SCS. And that's all that counts here. The historical evidence and legal case the Chinese present to support their assertion that they own damn near the whole sea are risible.
I picked up a copy of The Martian in my latest batch of books. I've heard some good things about it, so maybe I'll give it a shot before or after the Pakenham book.