It's not long form fiction though, it's essentially song-writing. The success of that genre, and it's exotic dimension, had a lot to do with its sentimental overtones (and erotic undertones), which was at the time quite disruptive. Socially it correlates with the rise of a new intelligentsia looking for more than the epic fiction that were the literary bread and butter until then. It colored the chivalric literature that came afterwards but even then the epic form remained the framework of reference.