Capitalism, unlike many religions, is testible and it's material in that it brings one material wealth. One of my favorite atheists was Ayn Rand who was pro-capitalist. She found capitalism to be very consistent with atheism. The existence of capitalism depends on individuals who think for themselves, who don't depend on an authority figure like a god or priest or politician. Individuals can't think for themselves if they are not free. Thus it is no accident that societies with greater freedom have more capitalism. Is capitalism a perfect system? No, but can you think of a system that has brought more material wealth to a greater number of people? And while you are pondering, how much material wealth has religion brought you?
Blame Hitchens, Dawkins & Harris...