DC fought a great fight. People just lost track of reality when they started believing he would demolish Jones, that is no easy task.
DC kept coming forward for the first 3-4 rounds, left it all in there and came up a little short. He took a LOT of strikes to his belly which I think is what took his pace down a bit towards the end, plus Jones leaned on him a lot and made DC carry his weight.
Jones used his size well to retain the belt. DC did the best he could with the very special skill set he has but it wasn't enough to overcome the HUGE size, age & reach advantages plus Jones diverse strikes, feints, head games, etc.
DC pushed Jones, that was a solid fight. Just because DC didn't live up to ridiculous and impossible expectations don't mean he didn't perform at an incredibly high level. Make no mistake about it, that was the arguably highest level of MMA competition that the world has ever seen.