What made you an atheist?

[Goosebump]

I read LOTR before I was exposed to any religion and LOTR was more believable.

[Magilla]

What, if anything, made you an atheist?

It's not necessary that anything makes one an atheist. Being atheist is the default position. Belief ought only to be held when there's good evidence for a position. In the absence of good evidence for a god (gods), one remains at the default of being atheist.

It requires something to make one become a theist and that may sometimes be with or sometimes be without good reason and evidence. When a religious person gives up their religious beliefs, then maybe a good question to ask is: "What made you become an atheist?"

I am an atheist because I find that in my experience, there is no good evidence or reason for god-belief, and because so many conceptions of what "God" is supposed to be are incoherent and/or contradictory.

[robvalue]

I read LOTR before I was exposed to any religion and LOTR was more believable.

Indeed. Far better written too.