Sometimes it is niche until technology catches up with a need.

Sometimes it is niche until an un-suckful product is actually offered.

Sometimes it is niche until a sudden shift in the entire economy or market.

The shift from horseshoe-clad transportation to a new thing was rapid only after about 20 years of "niche" gas-powered automotive vehicles.

My first thought was, someone who makes a hard-to-find part for a low volume vehicle. Take, for instance, the original Tesla Roadster. It sold about 2500 units. Maybe they have a problem that happens in 10% of units. You have a maximum of 250 customers, assuming none are scrapped and you provide the only potential solution.

These are the sorts of situations in which you’ll find very little competition. For a lot of people with niche interests there’s always “that one dude on the forums” who is the only person with the solution.

The same kind of situations arise often in enterprise too, and it’s the kind of things that internal teams or contractors might one-off. But, if you make an off-the-shelf product for it, you’ll be the only game in town!