Fans in San Diego never showed up in force for the Chargers. Even when they were a perennial playoff contender, opposing team's fans would regularly turn Qualcomm into an away game for the Chargers. They also were always near the bottom in attendance, even with a winning team.
I remember a few years ago I read an article that was roasting San Diego fans cause when it would rain there, even just a little bit the stadium would be half empty for games, but teams that play in sub-zero temps will still fill their stadium.
San Diego would be amazing if enough people actually cared, but even LA has problems with a lot of sports because SoCal sports fans seem fairweather as hell, the only teams they seem to give a fuck about are the Lakers, the Dodgers, the Angels and USC football. Anything else they stay hot and cold for