Why does religion continue to grow?

[Esquilax]

I'm interested to hear your theories of why by 2050, contrary to 300 years of predictions, almost 3,000,000,000 Christians will be sitting in pews around the world praying for the salvation of your grand kids. 

Golly gee, you mean a movement committed to cultural dominance, that routinely indoctrinates children into believing in it unquestioningly and backs up that demand for a total lack of resistance with threats of hell and, in some cases, social ostracism and other sanctions, that appeals to the least rational parts of our mind and reinvents itself utterly to take fiat credit for every secular social movement might, by hook or by crook, continue to grow? Who would have thought?!

Of course your religion isn't going to instantaneously shrink down to nothing; it has some of the most vicious mental hooks and self-reinforcement baked into it from the beginning, candy coated into supposedly good things by people trained for generations to swallow the doublethink it demands without question. It's going to be a long road, but I promise you this: the mainstream churches being attended in 2050 will be damn near unrecognizable to a christian from the year 2015. That's the nature of a church that remains amorphous enough to remain vital; it may not be getting strangled to death by the myopia of its own ideas, but it has no character of its own beyond the blandest of pablum.