Spain has had a strong democratic undercurrent for many years and at least since the 1530 Revolt of the Comuneros in Castile y Leon and the Revolt of the Brotherhoods in Valencia at the same time which almost saw off Charles V (a usurper and arguably protoEUite!!).
Part of their grievances related to overtaxation to fund Hapsburg territorial ambitions. The slave mines of Potosi in the Viceroyality of Peru saved Charles.
Spain hasnt any colonial silver supplies left now and shipments of gold from Bruselas have also ceased.