It soon became clear that the Inquisition, based on purifying Catholic Doctrine, could only be applied to Catholics. Thus, in order to catch everyone in their net, they forced non-Catholics to convert. However, once converted, the Inquisition then used their non-Catholic heritage against them – so they could not protect themselves or their descendants in any event.
In 1492 the Catholic Kings expelled the Jews and the Muslims from Spain. Some stayed on and became covert converts – even becoming Catholic religious leaders.