After the Spanish drove out the Muslim invaders Ferdinand and Isabella implemented a set of laws requiring any business persons buying or selling to be practicing Catholic or leave Spain.
They wished to ensure that Spain would remain Christian. To do so in their minds they needed to drive out non believers.
Before the Islamic invasion Spain was very tolerant to Jews.
Ferdinand solicited from Rome permission to enforce these laws with the Inquisition.
What is also not commonly known is that the Inquisition only prosecuted Jews that had been baptized Catholic but still practiced Judaism in secret. The numbers of Jews killed by the Inquisitions have been greatly exaggerated.
Thank you very much for that reply.
I had never looked to the cause of the Spanish Inquisition.