Novell basked in a near monopoly on networking and built a very successful sales channel based on authorized dealers.**
When a credible challenge finally came, they had no idea what to do about it. Ray Noorda went out and bought Novell a bunch of products to help build a competitor to Microsoft's successful integrated approach. Management hadn't one clue in hell what to do with these products and proceeded to pretty much destroy them all: WordPerfect, DR-DOS, Multiuser DOS, BTrieve, Unix, etc..
Yes, they survived, and have some promising products, but they burned through one hell of a lot of legacy market and a few management refurbs finding stability.
Microsoft has additional problems. Not only are they accustomed to monopoly control, they have a financial structure heavily leveraged by stock options and expectation of rapid revenue growth which will be painful to restructure under shrinking markets. They are also doing a good job of offending their customers and getting them to look at alternatives quite early in the game.
** Novel authorization made sure you could get authorized if you really wanted to sell their products. Hell, even I got authorized with little trouble.
In contrast, Banyon's dealer authorization process was designed to make it as difficult as possible to sell Banyon products. It didn't take a Microsoft to do them it, they did it all by themselves.