Microsoft was a major contributor to IE's downfall, through their incompetence. Google is doing a much better job of not shooting themselves in the foot with Chrome.
Idk, Netscape Navigator was good, but then nothing usable came afterwards while Microsoft had IE4.
People hate on IE now, but there was a phase when IE was that best free browser and I say this as someone who breathed open source at the time and who was as Anti-Microsoft as you can imagine.
From how I remember it IE's downfall came after Netscape's.