The US DoJ's Janet Reno was a major factor. She forced Microsoft to sign a Consent Decree (1995?) that prevented Microsoft from tying separate products to Windows but allowed it to provide integrated improvements. The DoJ followed up with an anti-trust suit (on Netscape's behalf) over browser tying.
Microsoft won the browser case by 2-1 on appeal. However, all this bloodletting may have been a factor in Microsoft putting off the next browser, which eventually appeared in Vista. Which was late, following the Longhorn debacle, which prolonged XP's life, which enabled IE6 to get entrenched, which caused web designers so much pain.
The world might be a better place if the DoJ hadn't interfered, but we'll never know....
Otherwise, I'd have picked his first Bill Gates review as one of my favorite articles of all time...