Why atheism is winning is because when a belief structure has no empirical basis, it only survives by everyone agreeing to maintain the illusion that it makes sense. It is the emperor's new clothes syndrome. But such beliefs are highly prone to sudden collapse as soon as it begins to be pointed out that there is nothing there. Once a tipping point is reached, changes in unsupported beliefs (whether it be god or racism and homophobia) can occur very rapidly.
The communication revolution, in addition to spreading the ideas of modernity to an ever-widening audience, will create a greater awareness, especially among young people, that one's religious beliefs are largely a product of where one is born and brought up, and not because they are self-evidently true.. Once you give up the idea that your own religion is obviously true, it is a short step to not viewing religion as a source of truth at all.
On the level of simply ideas, religion is losing because fewer are converting into religion than are converting out, especially amongst the young. That is the demographic time bomb that is going to doom religion
Religion is clearly on the defensive partly because the new atheists have taken the arguments against god out of the academic and philosophical and theological arenas and put them out in the public sphere and into the hands of ordinary people, and they are able to confront believers much more confidently.
I met Professor Mano Singham in my travels recently. He is a delightful man. We traded books. He has a great deal to share and I look forward to reading his blog as often as I can. As an introduction to him he has written eleven blogs on why atheism is winning that I think are great (seen in reverse chronological order). In his concluding post he writes: