Everything is going swimmingly. You are killing a debate with a Christian and the ‘I was once an atheist like you’ card is slammed onto the table.
Kapow! All the relevant haymakers you were setting up have turned to dust. If the theist knows where you are coming from and still chooses to believe, what are we missing here?!
One possibility is that many of these freebirds rebelled against God in their teens. Like they did with their parents, teachers and society in general. At a fragile age where our thinking has not had the time nor understanding to dive the depths reached later in life. Leaving adolescence, we are hit with increased responsibility and financial pressures. We are made to stand on our own two feet and rely less on others. It is likely there has been an increase in the loss of loved ones. Is it surprising that those that claimed to be previously atheist found a need for religion and a sense of guidance?
I wouldn’t expect anyone in their teenage years to have the answers. C.S Lewis is a name that is thrown about regularly in Christian circles. He returned to Anglicanism at the age of 32 after leaving religion in his teenage years. To compare a Godless, teenage C.S Lewis and his adult spirituality would be unfair in my opinion, for the reasons mentioned above. I haven’t studied his life, however I am sure this trend occurs regularly in many lives.
I have encountered many people that claim to have once been Godless, before abandoning reason and a world understood via evidence. What would it take to adopt faith, other than an overwhelming urge to feel loved during the difficulties of adulthood?