Netscape didn't attack Microsoft's business software, operating systems or other pieces of their offerings.

Google also didn't seriously attack Microsoft's business.

And neither had the capability to build large software very fast.

Google is both a software company and an infrastructure company as is Microsoft today. Their software is going to become more of a commodity but their data centers still have value (even perhaps more value since all this new software needs a place to run). It's true that if you're in the business of hosting software and selling SaaS you have an advantage over a competitor who does not host their own software.