Microsoft didn't invent C++, but they started with C which wasn't niche anymore at the time. So you do have a point here. However, you don't see big companies

Microsoft didn't invent C++, but they started with C which wasn't niche anymore at the time. So you do have a point here. However, you don't see big companies emerging that often anymore nowadays, so that could be a factor as well. And you don't see many startups relying on TIOBE either. Every place where programmer productivity is critical to the company's success is where you'll see niche languages used the most. If startups would stop getting acquired as soon as they get profitable maybe we'd see big companies emerging while using niche languages.