Can't think of a market where there's only one team and it's NFL off the top of my head, other than Jacksonville. Even Buffalo has the Sabres, for what that's worth. So that's not really an excuse. For football, LA is fairweather. No idea why, but it's been that way my whole life.
I don't blame it on "fair-weather" anything. The NFL is a different beast no matter what city you are in. Plenty of big marquee teams get run over by other marquee team's fans in their own building all the time.
It's just that it's amplified more because this is Los Angeles. The fact of the matter is it's happening all over the league.
Sorry, should clarify by saying not just one pro sports team but “small market.” Green Bay, Buffalo, New Orleans, Jacksonville, Kansas City, Indianapolis, Cincinnati, Cleveland, Tennessee, Pittsburgh...NFL is the main draw in each of those cities.