https://felsqualle.com/posts/2022/12/16-bit-support-in-64-bi... is the full story.

but tl;dr is that ntvdm relied on the CPU running 16-bit code, so was naturally EOL on a 64-bit Windows, where that mode doesn't work.

winvdm adds it back via CPU emulation.

I remember the post I read being a black themed site but this is also interesting, thanks