People are leaving religion because the facts as revealed by modern scientific evidence as well as continued archaeology and the indisputable geological record of this planet continue to disprove 'intelligent design' of any means as well as the bible and other religious texts; they fall more in line with a sometimes violent (mutation) but mostly painfully slow evolution over eons of time. It does not 'jibe' with religion in almost any form so people are leaving it behind. It's a good thing. The most religious countries on the planet are the most illiterate, violent, backwards and economically desolated communities whereas the more secular countries have a more stable community across the board.
There is a reason we call the most 'religious' time period in Europe "The Dark Ages." Religion devastated the continent. We are still paying the cost in modern times of that evil time.