Studying it all from an unbiased context you should see that is true, perhaps you don't realize this, but a large driver in the successes and failures of cultures spreading was geography and resources and certainly not the validity of the religious traditions of the surviving cultures which determined this.
It is the naturalists whom realize the world for what it truly is, based on evidence. There is no evidence for any kind of life after death, no evidence for reincarnation, of becoming an avatar, or anything like that and therefore naturallists tend to reject supernatural beliefs. Rather, for the here and now naturalists realize that we should love ourselves, obtain intellectual enlightenment via studying maths and sciences, get a nice home with a nice garden, earn plenty of money, innovate to make the world a better place, make friends and acquantences, raise a family, and then when it's all over your material self gets recycled by nature while your ideas and innovations, your genes, memes, and temes go on evolving for however long causality will allow them to. If you really believe however, that you're going to get an eternity of intellectual enlightenment AFTER you die, then go ahead and believe that, but there is no evidence for it.