An interesting aspect of our human wiring is that people love stories. I recommend the book The Storytelling Animal if you want to explore that idea in more depth, but it's just as easy to look around at all the way people enjoy stories in daily life. It's a big, Big part of how children engage with and learn about the world. Videos of all kinds involve stories. It's natural for kids to be attracted to them. And because they're stories, they're also rich in language, imagery, linear sequencing, culture, history, and social information. They are, in fact, full of the things kids need to develop literacy. At the same time, they're full of music and visual art - they're really incredibly rich experiences. It's no wonder kids forget to keep up their company face when watching - there's so much to experience!
One of the really interesting things about the way we process stories is that they're not lessons - we don't take them in as some kind of prescription. We use them as a way to play with thoughts, to bounce ideas around - and that's true for children, too. With kids, you often see that in very tangible terms - kids get up and play out things they've seen. Culturally, we're told that's bad, that it's some kind of detriment to imagination, but in very real terms it is imagination - it's the human mind performing it's greatest trick and acting as more than just an input-output box. So if your kid has favorite shows, be open to talking and playing about those shows. Don't make it a teachy thing - let your child take the lead and follow their natural tendency to form connections and make associations. See where their imagination takes them! It may seem very repetitive, especially at first, but it can be a kind of magic window into what your kid finds interesting and significant. It may surprise you! Little kids can be attracted to very big, dark ideas, like the nature of good and evil, life and death, right and wrong. It's a good chance to really appreciate how wonderful and complex your little person really is on the inside