Picture 1: Here are all 29 videos at the Imiga Kiken channel, as they look after clicking on "VIDEOS"; "SORT BY"; "Date added (newest)". [No surprises here]
Picture 2: And here are all 29 videos as they look after clicking on "VIDEOS"; "SORT BY"; "Most popular". [WTH!? Only one video visible!?]
But how can this strange situation possibly occur??
Well, "most popular" means most views over a certain recent time span. Suppose that 28 out of 29 videos have been kept private the last 90 days as countermeasure after a sexual content delete by YouTube. This would mean that those 28 videos would have zero views the last 90 days, and thus zero popularity the last 90 days according to YouTube's algorithms.
And videos with zero popularity WILL NOT become visible when the videos are sorted by "most popular" at YouTube.
So this seemingly odd sitution is actually the least odd possible outcome, that occurs every time a YouTube channel makes long time private videos public anew.
To see how many hours this effect will last, take a look for yourself HERE: https://www.youtube.com/channel/UC5M5hlMQjhR_QvoRoQ1aD7Q/videos?view=0&s... ?
UPDATE: This effect went away 32 hours after the videos were made public anew.
Furtermore, videos with 'zero popularity' will not be suggested to anyone by YouTube's suggestion algorithms. So if you do a three months emergency shutdown of a channel, then it will in practice take 3+2=5 months until the channel is back on track again, because it takes approximately two months until the suggestions have kicked in again as previously.
(BTW, "Sexual Content" deletes have been renamed to "Community Guideline" deletes (in 2017?), that in addition to sexual content also includes hate speech such as this meanspirited Len Kagamine song: https://www.youtube.com/watch?v=JsP1JENhbmg ).