They were king of the PC, imposing a Windows (and Office-) tax on every other business. They were trying to extend that dominance to the internet: Internet Explorer, CitySearch, Expedia, MSN portal, MSN Shows, MSN Messenger, you name it. They were building interactive TV, software for cars, and a mobile phone platform. For a while they were building a bill presentation and payment service. They had an e-reader platform and tried to sign up publishers for it.
You name, if it had software in it, Microsoft was trying to dominate it. They knew they were the new IBM and that IBM had stumbled, and they were paranoid about that happening to them. And here we are.