To say it's "human nature" is a poor excuse.
I think better access to information is the primary driver behind the rise in atheism. Atheism isn't about wanting to "sin" it's mostly about skepticism of claims that do not meet their burden of proof.
If you watch (and you will not) Dr. John MacArthur youtube clips on evolution and creation, you will walk away profoundly impressed. You see, not all Christians are dumb.
The world has become less religious which has lead to godless philosophies like Communism and Fascism. Nonetheless, the religion that used to be powerful -is a massively distorted one (heaven and hell teaching, papacy etc.).
I am not religious at all, and I am neither a communist, nor a fascist. The nations whose citizens enjoy the greatest freedoms are those with secular governments. The societies with the greatest societal health are those with the least amount of religiosity. Religion simply does not promote freedom or happiness. History shows this quite clearly.