It’s how you work it.
If I were a general contractor, I would only make one thing: tree houses. My niche would be the people who want to have a (minimum) $20,000 tree house built in their backyard. I’d need to find about 15 of them a year, and as long as they are willing to pay my travel expenses, they don’t even have to live in my town.
There are a lot more people who are going to hire contractors to build decks and sunrooms and renovate bathrooms, but I wouldn’t even consider bidding on that kind of work. I’m not interested in doing boring work where I have to compete on price.
I would only want to talk to people who want a tree house.
There is no such thing as a niche that’s too small if the people care enough.
If you think you need a bigger market, then what you’re really saying is that the market you already have doesn’t need you or depend on you or talk about you enough.
Unless your market has evaporated, then you probably don’t need a bigger niche. You just need to produce more value for those you already serve.