Railbird is right. It's not like the Chargers got dicked up and down the field in the second half...if anything, they benefitted from a few questionable calls that went their way (like the half-ass defensive holding penalty on third down when the ball was tipped at the LOS, which gave the Chargers new life on one of their scoring drives).
I took KC +15 for the game and doubled up by going with them +10 for the 2H. Granted, I was on the lucky end of an idiotic coaching call...but I could give you countless stories about my being on the wrong one. Anyhow, San Diego isn't playing well enough right now to be favored by that much over anyone, except maybe Oakland...