Comment by nalzok

  $ dig www.nyu.edu +noall +answer -t A

  ; <<>> DiG 9.10.6 <<>> www.nyu.edu +noall +answer -t A
  ;; global options: +cmd
  www.nyu.edu.            1       IN      CNAME   dsvdfvx64.github.io.
  dsvdfvx64.github.io.    2995    IN      A       185.199.109.153
  dsvdfvx64.github.io.    2995    IN      A       185.199.110.153
  dsvdfvx64.github.io.    2995    IN      A       185.199.111.153
  dsvdfvx64.github.io.    2995    IN      A       185.199.108.153

Looks like someone added a CNAME record pointing https://www.nyu.edu to https://dsvdfvx64.github.io, but https://github.com/dsvdfvx64 is 404. I wonder how one can use GitHub Pages while the corresponding username doesn't exist.