Everybody _he_ knew used WinAmp (in a time WMP was completely either useless or non-existent). About 40% of the people I know and work with would not touch Windows with a pole. Those do not make a significant cross-section of the market. Just like most people just lives with the OS their computer came with, most people just live with the browser that is installed by default either by the manufacturer or by their corporate overlords.
IE3 was the first "good enough" browser that came from Microsoft and, from 98 on, IE came bundled. For those who do not live in and for the web, "whatever comes with the computer" is what gets used. That was the last nail in Netscape's coffin.