What did the music really mean to the artists?

In the movie "Cadillac Records", in multiple scenes people were shown carrying weapons. And in one scene, Little Walter shoots somebody after getting in a very tiny argument, and it wasn't even that big of a deal. Using a popular name to sell certain products led to the death of the seller, because it was considered stealing the name and the music (I beileve). Did the musicians take that business that serious because of passion and love to the music or was it because they made a ton of money out of it and didn't want other people getting in their way?