Final answer:
After witnessing the horrors of World War I, many European Christians turned away from the church due to a loss of faith in traditional religious institutions.
Step-by-step explanation:
After witnessing the horrors of World War I, many European Christians experienced a collapse of confidence in the Church and turned away from it. The trauma and devastation of the war led some to question the effectiveness of the Church in dealing with the suffering and loss they witnessed.
This loss of faith in traditional religious institutions resulted in a rise of secularism and a decline in religious devotion among European Christians.