because of the weak PAC 12 South division and favorable schedule. They avoid Oregon and Stanford during the regular season and have a manageable OOC lineup: @ BYU, Northern Illinois, Idaho State. A good team should get at least 8 wins with their schedule, with the upside of 10+ wins and a PAC 12 South title, if they beat BYU in Provo and USC in Los Angeles.
Meanwhile, USC has to play @Washington, Oregon, Stanford, and Utah, along with a tough OOC slate: Fresno State, @BYU, @Notre Dame. UCLA plays on the road at each of Washington State, Stanford, Utah, and USC and plays Oklahoma, San Diego State, and @Cincinnati in the OOC.
Both USC and UCLA would have to overachieve just to get 8 wins. But, that's why they play the games....