Before Netscape, it was very difficult for people using different computer systems to access information on each other's systems. There was plenty of information on computer networks, but it was very hard for any one person to access it all. Netscape changed that.
What Netscape did was to use open standards to create a way for anyone to access all parts of the internet. When Netscape made this interoperable internet possible, and when they made it widespread by distributing their web browser very cheaply and often for free, consumers started to demand that other companies go along. This made the idea of open standards and an interoperable something that had to be adhered to by computer companies. They could not go back to creating separate systems that were not interoperable.