That's obviously not a requirement for becoming a professional musician.

Or simply not very good.

That, of course, is a bigger issue. But at the same time, it's really not that the people who make it are orders of magnitude better than the best ones of those who don't. Like in many other areas of life, there's factors other than excellence that play an important role, and a lot of them boil down to luck.

You can't get nowhere without some heavy-weight business insiders supporting you, even if you're that youtube wunderkind that then has a cinderella-like career. So much of a career is due to successful management, networking, and just being in the right place at the right time. Mind you, you gotta be good, and you gotta work, but that alone is not enough.