In the context of the people who did it, I think it’s just a “bit of fun”; a hobbyist hacking project to see how far you can take something.
But that said, it is absolutely insane how much disk space Windows needs. Windows Server 2022, with its most minimal “core” installation option, still has a minimum requirement of a baffling 32GB of hard disk space. By comparison, Ubuntu Server’s published minimum requirement is for only 2.5GB (with more specialist minimalist distros like Alpine coming in at well under 1GB).