10+ years ago, when most "grassroots" (and some of the better startup) hackathons were displaced by enterprise-sponsored hackathons. I can mostly talk about the Berlin hackathon scene, but as far as I understand it the same thing happened in SF/London as well around the same time.

Presentation-first judging has been a thing for a long time, and unless there is a organizing party that explicitly makes code reviews a part of the scoring, and the organizers ensure attendance quotas for different personas (engineer vs. product vs. designer) it will always drift that way.