Because of their location being quite central, and they are a mish-mosh of cultures, they appeal to almost all other countries in one way. They can be a hub as well as a great sightseeing place
Thanks for reminding that it had been a while since an update. Ethiopian has now moved up to 4th place! I guess they are in a good location to serve Africa (which has the most countries of any continent), Asia, and Europe! The top ten didn't change at all since 2019. They just switched some positions.