They were an uneducated atheist, when it came to historical facts, I think. There is no way to dispute historical facts. Once you study the origin of the Jesus Christ character and where it came from, you can no longer proclaim his existence.
Some people are atheists but have not thoroughly studied the origin of Christianity or whatever religion they proclaim.
I had a friend tell me she wasn't a Christian and was with me that Jesus didn't exist. Then she went to jail, prayed to God that he let her out in Jesus' name. Well, she was released the next day. So then she is a Christian again.
She was only non-Christian because she went off of what she heard me say. She never studied a thing for herself, which made it easy for her to go back.
I don't have a degree in psychology, but it seems to me that people who "find God" later in life after whatever else they've been doing usually do so because of some severe psychological stressor: divorce, death of a child, death of a spouse, a severe accident, being diagnosed with a terminal illness, etc. Our brains want things to "make sense" and sometimes the randomness of "shit happens" is just too much for people to bear, I guess. As someone else mentioned already, we seem to be able to convince ourselves of whatever delusion we choose to make us feel better.
With that said, I think if religion really had such a good deal they were offering, they wouldn't need to convert under duress.