Upon being crowned the shah of the Safavid Empire, fourteen-year-old Esma'il declared Shi'ism the official religion, which was a problem because the majority of his subjects belonged to what religious sect?

Upon being crowned the shah of the Safavid Empire, fourteen-year-old Esma'il declared Shi'ism the official religion, which was a problem because the majority of his subjects belonged to Sunni Islam.

Obviously, he couldn't have his subjects practicing a different type of religion, and thus a problem arose.