Talk radio and Fox news are highly popular. As I understand it, before he was fired, Tucker Carlson was the most watched news-related show.
I agree that there are popular progressive and left-leaning shows that focus on outrage (John Oliver, Jon Stewart, etc.) but as I understand it, they are not as successful or popular as Fox News and conservative talk radio.
My point was not that conservatives are more outraged than liberals (I suspect that each side sincerely believes that the other sides shows greater outrage). I just meant from a business perspective, it appears to me that the establishment cable news services are struggling to maintain audience loyalty which tells me that they are not as good as conservative media at taking advantage of audience outrage.