Bundling Excel and Word (and more) into a single MS Office product was a masterstroke that definitely helped them, but you can't claim that was some sort of evil monopolistic genius. They developed an integrated suite and that turned out to have value.
IE 4 vs Netscape 4 was a lot more complicated. They were technically fairly equal but Microsoft did everything it could to kill off Netscape, including many dirty tactics.
Windows XP was dramatically better than the first MacOS X iterations in almost every way except visuals. OS X had awesome graphics but the Mac hardware could hardly cope and it was dog, dog slow. It also had ~no apps and users frequently had to run productivity software in the Classic emulator.
Desktop Linux was a joke at that time and has never caught up. Basic things like "how can I install this program" or "why does my sound not work" were FAQs for Linux users in 2001, and arguably the community never really overcame its internal political issues to solve them.
BeOS had some interesting technical choices but its primary selling point was super-smooth multi tasking, which came at the cost of requiring app developers to all be expert at writing multi-threaded software, as the Be APIs practically required apps to be largely thread-safe. It turned out that requiring all your app developers to be in the upper percentiles of skill meant that you didn't get many apps and those that did exist were often unstable.
For all its faults and Tellytubby like UI, Windows XP had built on a legacy of slavish devotion to app and hardware compatibility, it hadn't jumped too far ahead of what the hardware was capable of, it was very developer friendly and it didn't have bizarre technical quirks caused by endless techno-ideological wars over packaging file formats and the like. That made it pretty successful.