Dave Cutler was very fond of MIPS and worked on that port, but I think it was done concurrently with the x86 version.

I don't think this is true. From what I can figure out, Windows was ported to MIPS, but had always been first done on intel hardware.

Do you have a link or reference for this? Curious.

It was originally developed for a Microsoft internal Intel i860 workstation, that's also from where the name NT comes from.