In 2016 a Pew Research Center survey received the following reasons Christians abandoned their faith:
Learning about evolution when I went away to college.
Religion is the opiate of the people.
Rational thought makes religion go out the window.
Lack of any sort of scientific or specific evidence of a Creator.
I just realized somewhere along the line that I didn’t really believe it.
I’m doing a lot more learning, studying and kind of making decisions myself rather than listening to someone else.
“Now it happened, as He was dining in Levi’s house, that many tax collectors and sinners also sat together with Jesus and His disciples; for there were many, and they followed Him. And when the scribes and Pharisees saw Him eating with the tax collectors and sinners, they said to His disciples, ‘How is it that He eats and drinks with tax collectors and sinners?’ When Jesus heard it, He said to them, ‘Those who are well have no need of a physician, but those who are sick. I did not come to call the righteous, but sinners, to repentance.’” Mark 2:15-17.
“This is He who came by water and blood – Jesus Christ; not only by water, but by water and blood. And it is the Spirit who bears witness, because the Spirit is truth.” 1 John 5:6.
“Therefore let that abide in you which you heard from the beginning. If what you heard from the beginning abides in you, you also will abide in the Son and in the Father.” I John 2:24.