This TedTalk goes into more detail, but basically there are a lot of sick things appearing on the Kids YouTube App. YouTube have absolutely NO WAY of controlling this.
There is 567,000 hours of video uploaded a day. There is not somebody sitting there manually watching and approving these videos, do you think they could even begin to afford the staff for this?
It works on an algorithm. The algorithm pics up swear words, controversial words in the video. It misses kids videos because most of these don't include speech. So they have to go on what the uploader has put in the title and tags, and the uploader will say it's suitable for kids.
The only way these video's get taken down is if they are mass flagged compared to viewership, and small children are not going to flag these videos, so they remain on the kids app.
Just to give some examples these violent ones both come up on the Kids App. I flagged them to YouTube and they haven't been age restricted / removed.
So they still appear on the Kids App. These ones are pretty tame compared to the more sexually themed ones but both appear on kids app when they're clearly not suitable. They appear on auto play and hence why they have millions of views.
I'm just warning people because they seem to think YouTube Kids is actually monitored properly when anyone can upload anything to it.