As mentioned in another comment, it started with bringing over a bunch of developers from Digital, hence why NT has a lot of VMS influence in its design. Per t

As mentioned in another comment, it started with bringing over a bunch of developers from Digital, hence why NT has a lot of VMS influence in its design. Per the Wikipedia page [1], the similarities became a potential legal liability, which Microsoft managed by continuing to invest in NT on Alpha. "Although they added the Win32 API, NTFS file system, GUI, and backwards compatibility with DOS, OS/2, and Win16, DEC engineers almost immediately noticed the two operating systems' internal similarities; parts of 'VAX/VMS Internals and Data Structures', published by Digital Press, accurately describe Windows NT internals using VMS terms. Instead of a lawsuit, Microsoft agreed to pay DEC $65–100 million, help market VMS, train Digital personnel on Windows NT, and continue Windows NT support for the DEC Alpha." [1] https://en.wikipedia.org/wiki/Windows_NT https://en.wikipedia.org/wiki/Windows_NT