This case went to trial by jury. They didn't settle w/ the DOJ and SEC. Andersen was allowed to continue auditing public firms until their conviction. Majority of their publicly traded clients left very shortly after the grand jury indictment was released before the trial occurred.
The Supreme Court ruling doesn't mean Andersen is not guilty. The justices threw out the conviction due to a technicality. They do this on many of the cases they hear.
I agree with your other comments. Large law firms also do the same thing.