The author is Grant Sanderson (https://en.wikipedia.org/wiki/3Blue1Brown) who has an undergrad degree in math from Stanford and worked at Khan Academy before starting his YouTube channel 3Blue1Brown. Also, the student who is mentioned in the video (Lisa Sauermann) as having solved this problem at the 2011 IMO (and attaining the only perfect score) just recently started as a Prof. at Stanford (http://web.stanford.edu/~lsauerma/) as a 27 year old.