I'm not sure and that's a good question but after a point it was a principle of saving them rather than caring them about. Probably a digital hoarding attitude.

Archive.org has it at least, everything from 2009 until 2023. But that's also need to be mirrored because can be taken down https://archive.org/download/jasons-all-sumo-channel-archive...

No! It would be easier but I burned myself so many times with removed videos that I do it on my own basically asap manually. Not a big deal once you have yt-dlp properly

I actually do! I have a perpetual VLC playlist which plays those videos randomly if I need some background noise.

I use yt-dlp (and back then youtube-dl) all the time to archive my liked videos. Started back in around 2010, now I have tens of thousands of videos saved. Storage is cheap and a huge percent of them are not available anymore on the site.

I also save temporary videos removed after a time for example NHK honbasho sumo highlights which are only available for a month or so then they permanently remove them.