Video wasn't great - considerably less than HD and frankly worse than most YouTube content these days.
Even when it's not great, the video quality is at least as good as sitting in the back of a meeting room, 50' away from a monitor showing a view from a poorly positioned camera whose operator doesn't really know what the demonstrator wants you to see.
Zoom and other meeting platforms (webex, etc) are quite different than youtube and other streaming services (netflix, etc).
Zoom will generally prioritize live and interactive over video quality, and probably prioritize audio over video.
Youtube (netflix, etc) can buffer (delay) content to "ride out" connection issues. You don't really care if your movie is delayed by 15 seconds, but a 30 second delay (2x15 sec each way) in asking a question of a demonstrator and getting an answer (even if it's the moderator asking) would be quite irritating.
In my experience (as both a demonstrator and attendee of remote demos), the live/interactive part is important.
Maybe there's a better choice for a large demo like this, where it is by nature a bit less interactive. But "live demos" is probably not a big enough market to justify the hardware and software development for a specialized platform.
Also there really was not that much time to evaluate alot of alternatives.
IMO Zoom was a good choice as most remote demonstrators are already using it, and have significant investment in both the hardware/software and the practice controlling zoom cameras while talking about what they're doing while turning - it's some significant multitasking that doesn't come naturally.
If you're on a meeting and have poor video, but others say they're ok - one thing to try is disconnect and reconnect. Sometimes (not always) the problem is in which exact server in zoom's network you get connected to (and the path the internet takes to get you there). So re-connecting can
sometimes get you a fresh "line" into zoom.