The issue was a regenerated church membership
One of the main results of the Great Awakening was the fact that it produced approximately 100 separate Congregational churches that left the Congregational Denomination, known as “New Lights” over a period of twenty years. The issue was a regenerated church membership, in that the Congregationalists had fallen into the apostasy of infant baptism. Estimates were that as many as fifty thousand were saved, either directly under Whitefield’s preaching or revivals spawned by others that were influenced by him. Out of this group of churches fourteen went further, were publicly immersed and became Separate Baptist Pastors. Two of these were Isaac Backus at Bridgewater, MA on April 13, 1748, who became the great Baptist historian and Shubal Stearns at, Tolland, MA, on March 20, 1751, who became the pastor of the famed Sandy Creek Baptist Church in Sandy Creek, N.C., that launched the Baptist churches of the south. There were two primary reasons why these Separates became Baptists. First, Separates had become Biblicists. The Bible had become their only rule of faith and practice. Therefore infant baptism could not be defended scripturally. The second was for economic reasons, Baptists could claim the Toleration Act, and be excused from supporting the State Congregational Church. However Quakers were excused too but few became Quakers. It was the Baptists that became the stimulus for the ongoing of the Great Awakening as it moved southward.
Dr. Greg J. Dixon, adapted from: This Day in Baptist History III (David L. Cummins), pp. 110 – 112.