PhD Musings: From Hinduism to Atheism: One person at a time
I would say that I was a believer initially, then became an atheist and now back to Hindu beliefs. If you had studies Hinduism carefully, you would have realized that even if you don't believe in all the Gods in Hindu mythology, you can still be a Hindu. Advaita, Bhakti and even Arya Samaj like thoughts are all different forms of Hinduism. The faith in God is a waxing and waning phenomenon for many. The true reason could be just as simple as lack of in depth knowledge in their religious faith. In times of doubt, only a realized guru can clear all the doubts in mind and guide the soul towards divinity.
I remember a friend of mine who was a practising Hindu. I asked him if he believed in God. He said no. Then why do you go to temple and follow customs; I asked. The reply he gave me made me think about faith in religion. Hinduism is a way of life and he found it comfortable to live that way. He could not think about living without going to temples, rituals and all the traditions. He himself believes that one day he might get his faith in God back. You don't have to be a christian to celebrate christmas. People of all faith celebrate Hindu festivals like Onam in Kerala.
It is natural for people to have less faith or no faith to God in times of happiness and prosperity. It is for the same reason, there are instances in Hindu mythology where devotees have prayed to God to give them misery and sadness so that they can always live in the remembrance of God.