What that does not explain to me is why Rosberg wasn't really into trouble (Brawn claimed he was, after the race, but during the race not one single message was directed towards Rosberg that he had fuel issues, while they went crazy with it on Hamilton's radio. Nobody with a healthy mind believes that Rosberg had fuel issues).
Either they splitted the strategies, with Hamilton boarding less fuel and hoping for rain, with rosberg being the "safe strategy" and having dry race fuel levels.
OR
Rosberg was able to save up all that fuel to make up for the deficit. I feel that is less likely, because Hamilton had to start saving fuel at an early point; I don't see Rosberg saving up that much fuel.