The Inquisition was premised upon political intrigues.
As The Jewish Encyclopedia notes (1906 ed. Vol. XI, p. 485),
It remains a fact that the Jews, either directly or through their correligionists in Africa, encouraged the Mohammedans to conquer Spain.
Also, note that Henry Kamen conducted research on the Spanish Inquisition and found that 2,000 people were executed over a 350 year period—that is just over 5 people per year. That certainly is 2,000 too many yet, nowhere near the over the top exaggerations about which “everyone knows.”
Specifically, he notes,
…during the sixteenth and seventeenth centuries fewer than three people a year were executed in the whole of the Spanish monarchy from Sicily to Peru, certainly a lower rate than in any provincial court of justice in Spain or anywhere else in Europe [p. 203]
In his review of Henry Kamen’s The Spanish Inquisition: A Historical Revision, Richard L. Kagan (professor of history and director of the Program in Iberian and Latin American Studies at Johns Hopkins University) noted:
…for centuries it [the Inquisition] had been associated primarily with the persecution of Protestants… following an initial burst of activity against conversos suspected of relapsing into Judaism and a mid-16th-century pursuit of Protestants, the Inquisition served principally as a forum Spaniards occasionally used to humiliate and punish people they did not like: blasphemers, bigamists, foreigners and, in Aragon, homosexuals and horse smugglers…
an all-powerful, torture-mad Inquisition is largely a 19th-century myth…
Philip J. Sampson has a great and detailed section on the Inquisition in his fascinating and very informative book 6 Modern Myths About Christianity and Western Civilization