Conversation so far:
What did Isabella I of Castile do in Isabella I of Castile's later years?
Isabella received the title of Catholic Monarch by Pope Alexander VI.
Why did she receive this title?
Isabella and Ferdinand embarked on a process of spiritual unification, trying to bring the country under one faith.

Question: Was this a successful endeavor?
Self-contained rewrite: Was Isabella and Ferdinand's attempt to bring their country under one faith a successful endeavor?