The collapse that CBS is seeing has been a long time coming. If your audience is aging outside the target demo, sooner or later the strategy of getting a mass audience to compensate is not going to work. They should have been thinking ahead long before now, figuring out how to shift into a new audience, instead of producing more cop shows and sitcoms.
FOX Is also in trouble but in their case, they did it to themselves with a new slate of shows even worse than their competitors. Where was their Last Resort
type attention grabbing action show for their male audience?
More on the topic here.