Tell me how the secular world is rational now that it is free from religion?

Not really rational, but it's demonstrated that the average human being is so incapable of virtue and so animalistic, that they probably do need an Argumento ab Deus code of morals imparting unto them the fear of eternal damnation (Christianity) or civilzation suffering the wrath of the Gods (any polytheistic religion, and something the Abrahamic God hasn't done for centuries now), in order to keep society stable. It speaks volumes about "God's creation".