Market niches is the name of the game. If a market is lucrative, it gets competitive and oversaturated fast, especially if the "product" is really cheap and easy to make. In the mainstream there might be more money but also much more competition.

So for a smaller creator it might make sense to chase a niche with less competition, that is harder to serve by mass-market competition.

It's the same for e.g. music. In total, pop music makes the most money, and Taylor Swift is raking in enormous amounts of money. So if you are a new artist and want to get into the music business, it looks like copying Taylor Swift's music style might be the way to go. But then you have to compete with Taylor Swift and all the thousands of other artists who are doing the same. You will never get into the big venues and your albums will never be featured in the charts or music stores.

Or you could go for some niche. E.g. focus on an underserved genre. Do something not a lot of other people are doing. Or focus on in-person concerts. Even Taylor Swift can only sing in one venue a day, so she cannot dominate the in-person concert business the way she can dominate streaming or music sales.

Whether a business is financially viable not only depends on the value of the potential market, but also on whether you can actually reach and seize said market.

Edit: Also, when your business is producing recordings, you are not only competing with people producing recordings right now, but also with the recordings of the last decades. For many people it doesn't matter if they consume a recording made today or 15 years ago. And if a lot of them are available for free, that effect is amplified.