Norman is a great place for college football. People REALLY care about Oklahoma football in Oklahoma and the boosters will make things work. Norman isn't some small town in the middle of nowhere, it's a great college town that is also a suburb to OK City (1.5 million people in the metro area). It's full of boosters who will throw some cash around.
As far as USC? The fan base isn't the same. LA is a draw for people but people don't really care about college football in LA. If they can catch lightening in a bottle and re-create the Pete Carroll teams, maybe, but I don't think it's possible.
IMO, Lincoln Riley left because they just made Oklahoma into the Florida job. There are going to be unreal expectations because it's Oklahoma and losing to Georgia and/or Alabama is going to eventually get you fired (sooner rather than later). At Oklahoma, before the SEC, you could win 10 games on a down year. At USC, Riley is hoping to recreate that for long enough to bolt to the NFL. Oklahoma went from being a fantastic job (with tons of job security) to a pressure cooker by joining the SEC.