For all of human history, we've been making music and art. And for almost all of that time, it was done for love of doing, not money. For a few hundred years, there was the patronage era, where if you were really good you could get a rich person to feed and clothe and house you while you made art. Or you traveled around giving performances for money or food or clothes or shelter. Then only in the last 100ish years ha…
To add another point on top of yours - something else to consider is that music used to be considered free. Or stated another way - without ownership. Society was the owner historically. I'm not knowledgeable enough to know the reason why this was the cause, but I've heard it talked about by historians in documentaries. I suspect it has to do with what you said - that wealthy people funded their artistic endeavors and society as a whole owned the result. Or that they weren't bankrolled by a rich person but instead collected money from passers-by on the streets as they performed. This also speaks directly to the concept of "traditionals" with no known authors.