Final answer:
Edgar Allan Poe chose the Spanish Inquisition as villains for its historical notoriety in brutal tactics and religious persecution, aligning well with gothic themes and exploiting the 'Black Legend' narrative used by England against Spain.
Step-by-step explanation:
Poe may have chosen the Spanish Inquisition as the diabolical villains in his story to exploit the notorious reputation of the institution and its historical association with extreme torture, religious persecution, and death. This reputation was immortalized by the so-called Black Legend which depicted Spaniards as merciless conquistadors, a narrative leveraged by Spain's imperial rivals, notably the English, during their own era of exploration and colonization.
The Inquisition's brutal tactics and the moral panic it engendered made it an apt symbol of horror and tyranny, serving as an excellent backdrop for a gothic narrative. Poe's choice echoes a broader cultural sentiment that was still prevalent and resonated deeply with audiences' fears and sense of injustice.