Many lawyers are hesitant to sue other lawyers, just like many pilots don't like publicly bashing other pilots. But there are other lawyers who specialized in malpractice claims. Finding them is no secret; they advertise. Also, like any specialty, if you call the wrong guy, he's not going to be interested.
One could surmise that a lawyer stealing client funds probably doesn't have much in the way of assets to go after. Judgment-proof defendants suck, whether they be lawyers or not. And insurance usually doesn't cover intentional acts, especially overtly criminal acts.
Yeah, well, you could always head down to the JP courts around here. Most of them are not lawyers. Any guesses as to whether that makes them better judges?