I wouldn't say there would be a chart, but maybe multiple charts, because many peoples experiences are different. I'll give my story as an example. Unfortunately for me, it was a pathetic, selfish, and very weak reason and the kind of thing /christian/ assumes all atheists are like.
For most of my life, I didn't entirely connect with Christianity. It didn't make sense to me, and I didn't want to admit out of fear that God was a gigantic dick. I didn't understand why I was supposed to love someone I had never seen before. A lot of sermons had contradictions, and so much shit didn't make sense.
I would have probably stayed an unempathetic christian for a long time out of fear though if the revelation that I liked loli (at the time) didn't shake damn near all the foundations of my life. I realized if I told any of my friends this they would disconnect from me, and if I told a priest this in confession, I could pretty much kiss the rest of my life goodbye. There was nowhere for me to go, and I can't count how many freakouts I had during that time.
Since I had nothing to loose at this point, I started to remember all the shit about religion that just didn't make sense, and I realized that the only reason I stuck with religion was because I was afraid God would kill me if I stopped believing. I was still going though freakouts at the time… but at least one thing brought a bunch of clarity to my mind, and that's that the christian religion was a bunch of probably manmade (or misinterpreted) bullshit. But unfortunately for the longest time after that I considered myself agnostic, because I believed picking any side was foolish because there was a chance everything I saw in front of me was just my perception, and I didn't bother to do much thinking as a result. Even though Atheists thought I was foolish, I still thought they were cool though, just not quite on the right track.
But then I found out that most atheists are technically agnostic atheists, people who can't truly prove that there isn't a god, but heavily lean on what we have found. I thought "Sure that makes sense, go with what is the most logical." Then bam. Here I am. While I have a long way to go, I've greatly come to terms with myself, the loli thing has mostly faded away, and while I am still really fucking depressed, I don't really see how lying to myself with religion is going to truly fix that, because my brain isn't wired like that. Not only that, but doing so would be absolutely pathetic, possibly even more pathetic than what led me question all this to begin. I'm sure I can find a way without lying to myself.
Sorry if that was TL;DR and cool blog, it's just that was my experience to show that it's kind of complex for a simple chart, and I'm sure many people's experiences are a lot different. There might be some similarities between everyone though.