TV networks often cancel profitable shows because they aren't profitable
enough. There are
enormous opportunity costs involved in allocating a network time slot to a show: you only get 24 hours in a day, and only a few of those are prime-time. If a prime-time show isn't making big bucks, you cancel it and try another one, and you keep doing that until you find a show that makes you say, "Hmm...if I cancel this, there's a good chance I won't be able to do better." Television networks, like big movie studios, are in the business of producing lots of shows, hoping for the occasional big hit.
If you're running a streaming service, the opportunity costs of a small-viewership show are much less. As long as you're making some money, there's no reason to stop. Because streaming services do not have to allocate broadcast time slots as a scare commodity, they can go with an entirely different model: many more shows, each targeted at a smaller but more passionate audience.