The secret to being the best in the world is to make the 'world' smaller.
Alan Scott was the best community-focused artisan pizza oven builder in the world. A niche that didn't exist before he got there, but one that spread, that engaged people, that created a tribe and that supported him.
Alan was passionate about his craft and wasn't shy about sharing it. He trained others, turned it into a movement.
It's entirely possible that you will choose a niche that's too small. It's much more likely you'll shoot for something too big and become overwhelmed. When in doubt, overwhelm a small niche.