What was main reason that Spanish rulers expelled Jews and Muslims from the Iberian Peninsula?
to strengthen the Catholic Church
to complete the Protestant Reformation
to increase the effectiveness of the Inquisition
to take revenge for the Crusades

To strengthen the catholic church.

Explanation:

In the 14th-15th centuries, say around 1492, this event of Jewish expulsion took place. And the primary purpose was to eliminate their influence on the Spanish population, and fight vehemently that its members did not start finding serious interest in Judaism. At this course, a lot of Spain's Jews had converted to Catholicism as a result of the religious persecutions they faced.

A great population of the Spanish Jews chose exile rather than the renouncing of their religion and culture, and the Spanish economy suffered with the loss of an important portion of its workforce. Many went to North Africa(joining up with their fellow muslims), the Netherlands, and the Americas, where their skills, capital, and commercial connections were put to good use.