For Apple Fitness+, it might sell more watches, but the reason it requires a watch is because the product includes sensors that read useful data during the fitness experience that other devices simply don't have.
Given Tim Cook has stated publicly that what Apple wants to be most known for when looking back on the company is improvements to people's health, I don't think Fitness+ was spun up to sell watches. It was created out of a genuine priority for the company to have a certain impact on the world.
I also don't believe the purpose of Apple TV+ and Arcade was to create Apple One. It seems like they genuinely are trying to come up with a unique service for these two areas. Apple One is just a bundling. They are also responses to growing problems. Apple Arcade is an answer to the growing problem of in app purchases and advertising. They want to create a pure, fun gaming experience that you can put in front of your kids and not worry about it. I think Apple TV+ is more about business deals required to build the Apple TV app itself. You aren't going to have a seat at the table if you aren't serious about buying and delivering content.
None of these were started because Apple thinks they could do better and contribute something, a word Steve Jobs likes to use. They are doing it simply because they needed those Services Revenue. Something to dilute down their near 100% App Store Margin and Google Search Placement.
Apple Music was something they wanted to save iTunes / Music as a Business. And they bought in Jimmy Iovine for that god damn "Next Song" idea.
Apple TV+ and Apple Arcade were part of the grand plan for Apple One. Unlike iCloud, Apple Music and Apple News+, Apple TV and Arcade does not have any per unit cost. iCloud are cost / GB, Music are cost per song played, and News are cost per article read. TV shows and Arcade Games are paid as a whole at a fixed cost regardless of users. This give opportunity for Apple to bundle them at a discount.
One could argue Apple Fitness+ is more like iTunes where it is used to sell more Apple Watch / iPod. And it isn't out yet so I am giving it some benefits of doubt.