I don’t have a physics background but I’ve always seen “c” as the speed of causality. The light happens to go at that speed in the absence of gravitational disturbances. Gravity and others fields should also move at this maximum speed.
That said, I’m still trying to come to terms with the fact that breaking this speed limit just means that causality would be potentially broken. Isn’t that just something we axiomatically believed based on experience and we just haven’t observed otherwise?