In Spain the King kicked out all the jews and muslims, so a lot of them "converted" this is right after the spanish monarchy took back a lot of land that was conqured by muslim nations. So there are a lot of new Christians and there are a lot of false converts, and it is the middle ages so there is still a lot of alchemy and witchcraft and superstition. the Inquesition was a reform movement to make sure that false converts were not curropting the Church and to make sure that people were not teaching heresy. It was a good idea but some of the methods were bad, although the forced confession was a normal part of medeival trials, you needed total evidence before someone could be found guilty, they did not really have CSI in 1492 so part of the evidese would be a confession