Why did Islam, which for a long time strengthened the spirit of the Ottoman army and helped its success

Why did Islam, which for a long time strengthened the spirit of the Ottoman army and helped its success, then ceased to play this role?

Due to the power and spirit of the soldiers, the supply of weapons, the Ottoman power, with a lag in development and prosperity with the leading European powers, could not become equal. Since not having the means to modernize their army, the importance of the empire declined. With each lost battle, the ranks of the Janissaries were rapidly thinning. which affected the material well-being of the army and the empire itself. The empire was unable to fully control and maintain its role as before.