Spain appears to have done what the USA is doing today, refused to change as the world caught up with it and then left it behind. This obstinence also showed up in fashion. Fashion then was more serious business than it is today because it served the role of advertising the wearer's, and family's/country's, power and wealth and as an aid in seduction, helping a woman find the best opportunity for her one available career. But Iberian style had a final burst of glory as depicted by Diego Velázquez and others. But it was old when Catherine of Braganza wore farthingales to Charles II's court in 1662. Iberian style closely followed French style in the 1700s with a few exceptions, such as the maja style.
But then following French style may not have been difficult because the Bourbons (Borbóns) took over from the Habsburgs and the French followed the tontillo style with supports called panniers throughout most of the 1700s.