No matter what organization, political activity, school, job or religion there are always those who are the "cream that rises to the top". Somehow their personality type coupled with their own personal circumstances makes it possible for them to go farther and longer than anyone else.
The Olympic hopeful who gets up at the crack of dawn to practice, works a menial part time job and sacrifices his personal relationships in order to achieve his goal. The little old lady who tirelessly volunteers to feed the homeless, cleans the church, visits the sick and is raising her 3 grandchildren. The highschool drop out who goes on to found a multimillion dollar enterprise.
When it happens among JW's they view it as proof of God's holy spirit in action and that theirs is the one true religion. If it was God's spirit causing this, why wouldn't everyone among his "chosen" people be able to do the same?