A question relating to El Clásico history for Spanish Real madrid fans

Hello Spanish Madridistas, I’m asking for a moment of your time in particular as I’d like an authentic Spanish perspective on the background of El Clásico, why it exists and how it influences and is influenced by past and present politics. This is for an essay titled “¿Hasta qué punto El Clásico influido por la política y la historia fascista?” And ideally, I’d like reasoning both for and against the influences. For example, tell me how deeply the rivalry stems from politics such as nationalism and the Civil War, but also tell me how the rivalry is simply down to good football, and perhaps even what you truly think of Barcelona fans (obviously be civil). All I ask for really is what makes El Clásico to you?