It was about 5 years between Netscape 4 and Mozilla 1.0. In that time, they lost about 80% market share.
It was about 5 years between IE6 and IE7. In that time, they lost about 10% market share.
Just in case there was any doubt about the argument that Netscape killed themselves, clearly there were other forces at work. It wasn't just down to a much criticized rewrite decision. Perhaps a better remedy than trying to get Microsoft broken up, would have been to insist on the default installation of an alternate browser.