Now imagine if your organisation scheduled work in such a way that this could have been done by a "1x engineer" during work hours, instead of relying on this chap to bang it out in the weekend.
It would never have been prioritized. The time to convince others that this was more valuable than other tasks would have far outweighed the time that he spent working on it on his own time. He thought it was a cool idea and just did it without seeking permission.