Entertainment—sometimes, just like God—works in mysterious ways. It’s like throwing spaghetti at the wall; you never know what trends will stick and which will not. There’s a very good argument to be made that when YouTube Red (remember that?) launched a sequel to “Karate Kid,” the chances it would last more than one season were very low. Damn! The chances that this new venture on YouTube will last very long were even lower.

In theory, it sounded like a great idea; then again, when you get something for free, it’s hard to convince people to pay for it despite all the best efforts. Six seasons later (one could argue they were at least a season too long), “Cobra Kai” proved to be so much of a success. Its blend of teen soapy melodrama and some solid fight choreographies was quite engaging. There are very few...