This was fun to read! You convey the ferment of music at the time. One thing many people don't know is how big and important New Orleans used to be. It was once one of the 10 biggest cities in the US. I'm guessing here, but it might have been the biggest port in the US until the Erie Canal allowed New York to eclipse it. As a nexus of water transport routes, it might have been unrivaled in North America at one time, as a "crossroads" of the Mississippi drainage and the Caribbean. The next big change would have been Chicago becoming a railroad crossroads for the larger Midwest, hence the migration of jazz to Chicago. (Someone please correct me on any of this as needed.)

In a way, it's useless to try to pin down "the originator" of almost anything. Isaac Newton said he stood "on the shoulders of giants." Rarely do heroes not have childhood heroes who inspired them. Innovators add twists to what they grew up with.