He explains why it’s unlisted in the first few minutes. Basically, he knows it’s too long for the regular viewer, and plans to release a condensed version later. But for the people who may be interested in a deep dive, he made the much longer unlisted version where he has the freedom to ramble and fully explain things.

As for why it’s unlisted, it’s probably so he doesn’t get dinged by the YouTube algorithm for incomplete views. If the algorithm sees that his regular viewers are only watching the first 5 minutes of his hour long video, it’ll stop recommending his videos to them. Unlisting the video is an easy way to get around that, because only the people who are interested in it will seek it out.