It also says it was uploaded to YouTube in 2013. Typical video resolutions were lower back then.
Or possibly via 16mm. I got similar vibes to a lot of the educational films from the 70s which I had to watch in high school in the 90s.
Maybe they didn't keep the original negatives, just a master tape to make copies from.
In general, when you're looking at video that old, you're almost certainly looking at multi-generation copies with some transfers being decidedly suboptimal. It's pretty unlikely that they have the original nitrate film.