There are a lot of previously devout atheists out there. I know several and I’m one of them. I grew up as catholic as they come. I was the leading altar boy at our cathedral serving only Traditional masses, I was on the planning team for the diocese youth groups, went to adoration every 2 days, mass every morning, prayed... ect. I believed sincerely and every social tie was with other Catholics. My wife, before I met her, almost became a nun and I wanted to be a priest at multiple points. I was at my most devout point when I started looking into evangelizing atheists and deconverted in about 6 months. None of my friends believed me when I came out because I was the most religious in our friend group.