Before I began to study philosophy in college, I already had a strong leaning towards an intellectually-oriented, even philosophical, Christian faith. I believed that there were good, solid reasons for believing in God, and in the inspiration of the Bible, and in the resurrection and deity of Jesus.
As I studied the arguments for the existence of God and the various objections that skeptics have raised to these arguments, it became clear to me that there were no compelling arguments for the existence of God, and that there were plenty of good reasons to doubt that such a being existed.
At the same time that my belief in God was being challenged by my studies in the philosophy of religion, I was also struggling with the idea that a perfectly good and perfectly just creator would consign some of his/her own creatures to eternal torment and misery in hell. I attempted to find alternative interpretations of the New Testament, so that I could maintain my basic Christian beliefs but discard the revolting idea of a loving parent who tortures his/her own children by burning them alive. This attempt was not successful. I was left with the firm conclusion that if the creator had indeed inspired the NT, then he/she must either be an evil and immoral person, or else be an incompetent bungler who unintentionally left the clear impression that he/she was an evil and immoral person.
Up until that point I had managed to ignore a number of apparent inconsistencies and absurdities in the Bible, but as I became open to the possibility that there were errors in the Holy book, a number of examples of such problems began to quickly pile up, and my dozen-year love affair with Jesus and the Bible came to an abrupt end.
Why did I reject Christianity? I rejected Christianity because there are no solid arguments for the existence of God, but there are good reasons to doubt the existence of God. I also rejected Christianity because the Bible contains a number of inconsistencies and absurdities. Most of all, I rejected Christianity because the moral principles that I learned from Jesus led me to the conclusion that Jehovah (the God that Jesus worshipped) was an evil and immoral person.