Those works are only readable by 5 million people. It’s a lot, but considering wildly successful products are seen by less then 1 percent of the population, that’s only 50,000 books. Not so good especially if sold over 5 years.
The medium matters. Perhaps someone who wants to be a writer who is Finnish needs to learn English, or Chinese! It’s not always fair where our starting points are, but if we are clear about our intentions and desired outcomes it’s possible to determine if learning English or Chinese is worth getting to where we want to go.