It might have been a great business, if the owners of those movies had been happy to just get a small fee from Netflix.
Unfortunately that's not how it turned out, for instance Disney decided they could both make their own tech and their own content, esp for such things like Mandalorian which takes a modern long-story format that is suitable for streaming. Basically it turns out content is king, which Netflix also realized as they went and tried to make their own stuff with limited success.
What I don't get is why it's so hard to make the content. They've certainly thrown a lot of money at it, how come nothing sticks? By contrast everything Disney makes seems to be high quality.