Let’s discuss Buddhism for example which I consider a peaceful religion from its inception to its present state. In its core value Buddhism does not believe in a supreme being, the philosophy is mainly based on living a moral life. However being situated in the Hindu cultural milieu of that time Gautama Buddha did strongly believe in afterlife and soul. Buddhism is more about attaining ‘Nirvana’ meaning freedom from the cycle of rebirths.
The best moral way of life is set forth by Buddhism and it’s pretty straight forward to a lay person to adapt and follow in life and technically Buddhism was against worshiping deities or following priests and very much a common man’s way to spirituality without any ritual or middle man.
Buddhism, spread to South East Asia from India, and has pretty much survived in South East Asia until the west rediscovered it and adapted it as we know now.
An interesting observation in recent years has been made by many is that learning from the Buddhist tradition various forms of meditation techniques are actually being used as quick fix to a stressful life. In a sense its still used as a caffeine to get re-energized and go back to live our materialist life, or as short term fix by doing meditation retreats and then going back to a life which might not really incorporate compassion and kindness in the way we lead our lives.
Also many atheists who have studied the meditation techniques and have devised their own non religious form of meditation techniques should accept the fact that their journey started from learning the great tradition of Buddhism, and in its own time it was indeed an atheistic belief system. And all the rituals, arts and paraphernalia and the monarchical system of Dalai Lama was added to the Buddhist tradition later on.