The NT kernel contains many fine things, but it was released in a badly immature state. Until NT 4, the multiprocessor support was unfit for purpose. DCE RPC was also broken. The publicly-available DDK documentation was insufficient for anyone to write a kernel-mode driver. If you wanted the real doco, Microsoft would sell it to you under NDA, but no one told you that. If they had had any real competition, the product would have discredited itself out of existence within two years.