Duarte, a theologian and director of the Fatima shrine museums, spoke about the cultural significance of the Miracle of the Sun given the atheistic thought prevalent in Portuguese society at the time.
In 1917, Portugal, like the majority of the world, was embroiled in war. As World War I raged throughout Europe, Portugal found itself unable to maintain its initial neutrality and joined forces with the Allies, in order to protect colonies in Africa and to defend their trade with Britain. About 220,000 Portuguese civilians died during the war; thousands due to food shortages, thousands more from the Spanish flu.
https://www.catholicnewsagency.com/news/miracle-of-the-sun-broke-darkness-of-portugals-atheist-regimes-28148