Keep in mind that LA/Orange County has quite a few pro and high level college teams to support. Lakers/Clips, Dodgers/Angels, Kings/Ducks, UCLA/USC. So it was folly to assume that two crappy NFL teams playing in crappy stadiums would immediately succeed just because it's the NFL.
LA is a Lakers, Dodgers, Kings and USC football town. That's it. Hell, even UCLA basketball has a hard time filling Pauley Pavilion and they're the most decorated college team in history.