The team moved to Oakland because the LA Coliseum was falling apart and Oakland promised renovations to Oakland Coliseum.
It will take a long time but there is no way an adult in Los Angeles will root for the Chargers unless they are already fans. If the Raiders had moved to Denver, would you expect Broncos fans to go to Raiders games? When the Rams were in "LA" they were actually in Anaheim. People in Los Angeles never cared for the Rams either. The Ram and Charger bases will take a lot of time to grow. For now it is still a Raiders town, and will be for 8-10 years or so.