Of course music is a competition, in listeners' time, sales, streams, and awards.
...where musicians are graded on how dramatically they slap comedians before receiving their awards instead of how good their performance was, and comedians are graded on how well they take their slaps instead of how much the musician who slapped them just laughed at their jokes.
Is it so unfathomable to you that people make art for its own sake?
No, it's not; in fact I do it myself. That doesn't change the fact that all artists are competing for the public's attention.
Many are compelled from within to create and they have progressed and developed to the point where their art appeals to a large audience — they do not produce out of competitive drive, but out of an intense inward force that they can only satisfy through creative expression. They are those who create because they must, not just because they can.