It was a multi-year project at Microsoft Research with a team of >100 developers.

https://www.zdnet.com/article/whatever-happened-to-microsoft...

I am very certain in my recollection that this was started much earlier than this as hackathon skunkworks before something like this happened at MSR. It didn't do anything beyond kernel and command line, there was no browser. I don't know if those two shared roots either. Anyhow, but yeah, still both were intellectual feats!