It's good that you don't believe everything that passes by. Apply that skepticism to the materialistic version of origins.
I did some checking and Voltaire's time-frame was 100 years till the demise of Christianity (not a couple of generations) which would have come to pass around 1880. His house was turned into a center for the distribution of bibles within 50 years of his death.
Let me know when you have a credible source.