Context · YouTube
YouTube is built to show your child whatever keeps them watching the longest, and what holds their attention is often very different from what's actually good for them.
Why this matters for your kid
YouTube measures success in watch time, so every video it suggests is the one most likely to keep your child watching, and the stuff that gets them worked up gets pushed more because it holds attention better. The app has one job, keeping your kid watching, and it does that job whether or not what it serves up is good for them.
What your child experiences
They start with a cooking video and end up watching conspiracy theories, and the app simply follows whatever holds their attention, wherever that happens to lead.
What you might notice
Check what they're watching about twenty minutes in, because the video they started with is usually harmless and the algorithm has already carried them somewhere else by then.