Which event forced artist of the Northern Renaissance to paint their religious symbols in a more secretive way?

The Reformation, particularly the rise of Protestantism in the 16th century, forced Northern Renaissance artists to adopt more secretive methods of incorporating religious symbols into their work. As the Protestant movement criticized the Catholic Church and its practices, artists had to navigate the changing religious landscape carefully. This led to the use of subtle symbolism and metaphors in their art, allowing them to convey spiritual meaning while avoiding direct confrontation with prevailing religious doctrines.