Rush and Hannity have an established market ... angry white males. People who feel "their" country is being taken away from them by minorities, women (or, as Rush likes to call them, "sluts" or "Feminazis") and, worst of all, Democrats.
They feed on the entitlement of their audience. Morgan never had that, because even the most liberal person on the planet can recognize he's a douchebag. Fans of Rush and Hannity don't care -- as long as those fans' problems are being inflicted on them by the liberal scourges, Rush and Hannity can say what they please without angering their fanbase.
ANECDOTE TIME: During the mid-to-late 1990s, my grandmother lived next door to me and my folks. And she'd always have Rush on the radio. Now, she wasn't a full on dittohead (although if she was still alive she'd STILL claim Bill Clinton had Vince Foster killed), but the stuff that came out of Rush's mouth was unreal. His entire show was telling angry white males how they're getting dicked over. Which, of course, is asinine.
Nothing I've seen or heard since has led me to believe anything has changed one iota. Sure, he's got female and minority listeners, but that's not his target audience. And Hannity is Rush with that extra bit of Irish belligerence I know all too well from my extended family.