Many people raised as JWs initially reject it, but some are drawn back because they still believe it on some level. Some come back when they have children, as they become afraid for them, some come back when they have problems, and some come back to make their family happy.
Many are brought back for the same reason as you, the dreaded "what if they are right?". I don't know your history, or why you left, but if you left because you didn't think it was the truth, why are you doubting it now? Do you understand cult mind control and how it works? Because that is what the Watchtower uses to keep people afraid to leave.
Why would you think there is any possibility that the Watchtower is God's only chosen organization? They lie about their history of past wrong predictions, they use cult mind control techniques, they hide child molesters and break up families with their harsh shunning practices. In my mind there is zero chance they are being used by God, so I don't waste time wondering "what if they are right?" anymore than I wonder "what if the moon is made of green cheese?"