logical reasoning.
People tend idolize celebrities. They desire to be like them. Many people often think that their lives would better if they more like this celebrity or look more like that celebrity. Many individuals try live, dress, and look more like celebrities to escape their own reality. People copying celebrities' beliefs or rather disbeliefs are simply trying to do this.
The media has a lot to do with the celebrity hype. They us what these celebrities are doing, saying, and wearing at all times. The media make these people out to be very important and something to be adored. The media also take the time out to tell the people these celebrities' personal and moral belief as if they are trying to stir us one way or the other.
Many people look at these celebrity atheists and begin questioning their own belief through plan old "logical reasoning. These people (celebrities) do not believe in God, yet, they are living the "good life". If God is not punishing them- does that mean that there is no God? They do so much good but they do not believe in God. This must means that you do not have to believe in God to be a good person and that you are a bad person simply because you not believe. Through these thoughts and many different variations of "logical reasoning" like these, people see atheism a simple choice not a life choice of moral continuity.
Many people for many reasoning have chosen to follow these celebrity atheists. Personally, I believe that every person most walk their own path. If the path of atheism is, the path for you then that is the one you must walk. Nevertheless, be sure that is your path not another's. And always keep in mind that you cannot find another person's peace.