It's interesting to me how many of us seem to have interpreted this question differently. The question has been variously interpreted as...

"what makes a song GOOD?" or
"what makes a song LUCRATIVE?" or
"what makes a song ENJOYABLE?" or
"what makes a song POPULAR?" or
"what makes a song INTERESTING?" etc

But the original question was specifically about commercial success. If you aren't making money, then music is a hobby not a business.

The question assumes the music is good, but then wonders why not all good music sells. This more of a business question than it is a music question.

Artists tend to be notoriously bad business people because they are too invested in their art to sell it objectively. For the same reason that you should let somebody else master your songs, most of us would be wise to let somebody else market our music.

The 1st question, then, is how to find a sponsor with enough influence to represent you effectively

The 2nd question is how to get noticed by that sponsor

My personal opinion is that sponsors look specifically for talented artists who are naive and easily persuaded to sign contracts that give most of the profit to the sponsor.

https://www.dropbox.com/sh/ey71h8ep047758h/AAC12jNM0Hz9Q8zsh5iDeqNHa?dl=0